Tissue ablation device assembly and method for electrically isolating a pulmonary vein ostium from an atrial wall

ABSTRACT

This invention is related to a tissue ablation system and method that treats atrial arrhythmia by ablating a circumferential region of tissue at a location where a pulmonary vein extends from an atrium. The system includes a circumferential ablation member with an ablation element and also includes a delivery assembly for delivering the ablation member to the location. The circumferential ablation member is generally adjustable between different configurations to allow both the delivery through a delivery sheath into the atrium and the ablative coupling between the ablation element and the circumferential region of tissue.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/435,281 filed on Nov. 5, 1999, now U.S. Pat. No. 6,652,515, to whichthis application claims priority under 35 U.S.C. § 121. U.S. patentapplication Ser. No. 09/435,281 is a continuation in part of U.S. patentapplication Ser. No. 08/889,798 filed on Jul. 8, 1997, now U.S. Pat. No.6,024,740; and Ser. No. 09/199,736 filed on Nov. 25, 1998, now U.S. Pat.No. 6,117,101, to which this application also claims priority under 35U.S.C. § 120. This application also claims priority pursuant to 35U.S.C. § 119 (e) to provisional application 60/133,677 filed on May 11,1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a surgical device and method. Morespecifically, it is a device assembly and method adapted to form acircumferential conduction block along a circumferential region oftissue along a posterior left atrial wall and surrounding a pulmonaryvein.

2. Description of the Related Art

Many abnormal medical conditions in humans and other mammals have beenassociated with disease and other aberrations along the walls thatdefine several different body spaces. In order to treat such abnormalwall conditions of the body spaces, medical device technologies adaptedfor delivering specific forms of ablative energy to specific regions oftargeted wall tissue from within the associated body space have beendeveloped and disclosed.

Cardiac arrhythmias, and atrial fibrillation in particular, persist ascommon and dangerous medical ailments, especially in the agingpopulation. In patients with normal sinus rhythm, the heart, which iscomprised of atrial, ventricular, and excitatory conduction tissue, iselectrically excited to beat in a synchronous, patterned fashion. Inpatients with cardiac arrhythmia, abnormal regions of cardiac tissue donot follow the synchronous beating cycle associated with normallyconductive tissue in patients with sinus rhythm. Instead, the abnormalregions of cardiac tissue aberrantly conduct to adjacent tissue, therebydisrupting the cardiac cycle into an asynchronous cardiac rhythm. Suchabnormal conduction has been previously known to occur at variousregions of the heart, such as, for example, in the region of thesino-atrial (SA) node, along the conduction pathways of theatrioventricular (AV) node and the Bundle of His, or in the cardiacmuscle tissue forming the walls of the ventricular and atrial cardiacchambers.

Cardiac arrhythmias, including atrial arrhythmia, may be of amultiwavelet reentrant type, characterized by multiple asynchronousloops of electrical impulses that are scattered about the atrial chamberand are often self-propagating. In the alternative or in addition to themultiwavelet reentrant type, cardiac arrhythmias may also have a focalorigin, such as when an isolated region of tissue in an atrium firesautonomously in a rapid, repetitive fashion. These foci may act aseither a trigger of paroxysmal atrial fibrillation or may sustain thefibrillation. Recent studies have suggested that focal arrhythmia oftenoriginates from a tissue region along the pulmonary veins of the leftatrium, and even more particularly in the superior pulmonary veins.

Percutaneous catheter ablation techniques have been disclosed which useend-electrode catheter designs with the intention of ablating andthereby treating focal arrhythmias in the pulmonary veins. Theseablation procedures are typically characterized by the incrementalapplication of electrical energy to the tissue to form focal lesionsdesigned to ablate the focus and thereby interrupt the inappropriateconduction pathways.

One example of a focal ablation method intended to destroy and therebytreat focal arrhythmia originating from a pulmonary vein is disclosed byHaissaguerre, et al. in “Right And Left Atrial Radiofrequency CatheterTherapy Of Paroxysmal Atrial Fibrillation” in Journal of CardiovascularElectrophysiology 7(12), pp. 1132–1144 (1996). Haissaguerre, et al.discloses radiofrequency catheter ablation of drug-refractory paroxysmalatrial fibrillation using linear atrial lesions complemented by focalablation targeted at arrhythmogenic foci in a screened patientpopulation. The site of the arrhythmogenic foci was generally locatedjust inside the superior pulmonary vein, and was ablated using astandard 4 mm tip single ablation electrode.

In another focal ablation example, Jais et al. in “A Focal Source OfAtrial Fibrillation Treated By Discrete Radiofrequency Ablation”Circulation 95:572–576 (1997), applies an ablative technique to patientswith paroxysmal arrhythmias originating from a focal source. At the siteof arrhythmogenic tissue, in both right and left atria, several pulsesof a discrete source of radiofrequency energy were applied in order toeliminate the fibrillatory process.

There is a need, however, for a circumferential ablation device assemblyand method adapted to electrically isolate a substantial portion of aposterior left atrial wall from an arrhythmogenic focus along apulmonary vein. In particular there is still a need for such an assemblyand method which provides a circumferential ablation member secured tothe distal end of an elongate catheter body and which includes anablation element adapted to form a circumferential conduction blockalong a circumferential region of tissue which either includes thearrhythmogenic focus or is between the arrhythmogenic focus and asubstantial portion of the posterior left atrium wall.

SUMMARY OF THE INVENTION

This invention is a tissue ablation system and method that treats atrialarrhythmia by ablating a circumferential region of tissue at a locationwhere a pulmonary vein extends from an atrium. In general, the systemincludes a circumferential ablation member with an ablation element thatablates the tissue at the location, and also includes a deliveryassembly for delivering the ablation member to the location. Thecircumferential ablation member is generally adjustable betweendifferent configurations to allow for in one configuration the deliverythrough a delivery sheath into the atrium, and in another configurationthe ablative coupling between the ablation element and thecircumferential region of tissue at the location.

According to one mode of the tissue ablation system, the circumferentialablation member is adjustable to a position wherein a circumferentialwall has a distal facing surface that surrounds the longitudinal axis ofa cooperating delivery member. The ablation element ablatively couplesto a circumferential area that is normal to the distal facing surface.The distal facing surface is configured such that the circumferentialarea coincides with the circumferential region of tissue when the wallis adjusted to the second position at the location, and therefore theablatively coupled ablation element is adapted to ablate thecircumferential region of tissue there.

According to another mode of the invention, a circumferential ablationmember has a circumferential support member that is adjustable between afirst position that is adapted to be delivered through a delivery sheathinto the atrium and a second position having a substantiallycircumferentially looped shape. An ablation element is locatedsubstantially along the circumferential support member and is adapted toablatively couple to a circumferential area adjacent to the supportmember in the second position. The looped shape of the circumferentialsupport member is configured such that the circumferential areacoincides with the circumferential region of tissue when thecircumferential support member is adjusted to the second position at thelocation. A positioning assembly that is coupled to the circumferentialsupport member such that the circumferential support member may beadjusted between the first and second positions when the circumferentialsupport member is substantially radially unconfined within the atrium.In addition, a delivery assembly cooperates with the circumferentialablation member and is adapted to at least in-part deliver thecircumferential ablation member to the location.

In one aspect of this mode, the circumferential support member has anelongate body that extends distally from a delivery member and issufficiently straight in the first position to fit within a deliverysheath. The elongate body is reconfigured into the looped shape forablation when the circumferential support member is adjusted to thesecond position.

In one variation of the system according to this aspect, the deliverymember has a passageway extending between a distal port adjacent theproximal end of the elongate body and a proximal port located along theproximal end portion of the delivery member. The positioning assemblyadjusts the position of the ablation member by use of a pull-wire thatis moveably engaged within the passageway such that the proximal endportion of the pull-wire extends proximally through the proximal port,and the distal end portion of the pull-wire extends distally through thedistal port where the pull-wire is secured to the distal end of theelongate body. In the first position the first and second ends of theelongate body are spaced along the pull-wire with the intermediateregion of the elongate body extending along the longitudinal axisadjacent to the pull-wire. The circumferential support member isadjustable to the second position at least in part by adjusting therelative position of the pull-wire with respect to its moveableengagement within the passageway of the delivery member such that theproximal and distal ends of the elongate body are longitudinallycollapsed toward each other. Such longitudinal repositioning of the endsof the elongate body cause the intermediate region to deflect radiallyinto the desired looped shape.

According to a further feature of this variation, at least one indicatorwhich indicates when the circumferential ablation member is in thesecond position, such as in one further variation by use of first andsecond radiopaque markers on the opposite ends of the elongate body, orby use of visible indicators on the proximal aspects that indicate therelative positioning of the pull-wire versus the delivery member.

In another aspect of this mode, the circumferential support membercomprises an elongate body with a distal end secured to the distal endportion of the first delivery member and a proximal end secured to thedistal end portion of the second delivery member. The positioningassembly comprises an outer member with a proximal end portion and adistal end portion that surrounds the distal end portions of the firstand second delivery members and that has a longitudinal axis. The distalend portion of at least one of the delivery members is moveable alongthe outer member, such that in the first position the elongate bodyextends distally from the first delivery member substantially along thelongitudinal axis, and in the second position the delivery members arelongitudinally adjusted relative to each other and also relative to theouter member such that the elongate body is positioned externally of thedistal end portion of the outer member with the elongate body adjustedinto the substantially circumferentially looped shape.

According to various of the modes and more particular aspects hereinsummarized, one further variation provides an anchor along a distal endportion of a delivery member associated with the system and which isadapted to secure the delivery member within the pulmonary vein whilethe circumferential ablation member is being ablatively coupled to thecircumferential region of tissue. In one more detailed example theanchor includes an expandable member that radially expands to engage thepulmonary vein in order to secure the delivery member in place duringablation.

In another aspect of this mode, the positioning assembly includes anarray of circumferentially spaced splines that are positioned around thelongitudinal axis. Each spline has a proximal end portion coupled to thedistal end portion of the delivery member and a distal end portioncoupled to the circumferential support member. Each spline is adjustablebetween a first configuration, wherein the distal end portion of thespline extends substantially along the longitudinal axis, and a secondconfiguration, wherein the distal end portion of the spline extendsradially away from the longitudinal axis. The first position for thecircumferential support member according to this aspect is characterizedat least in part by each of the splines being adjusted to the firstconfiguration. The respective second position is characterized at leastin part by each spline being adjusted to the second configuration.

According to one variation of the spline aspect of this mode, eachspline provides a single elongate member that terminates distally whereit is secured to the circumferential support member. In anothervariation, each spline provides a looped member having an apex along thedistal end portion of the spline and two legs extending proximally fromthe apex along the proximal end portion of the spline. Further to thislatter variation, the circumferential support member is threaded throughthe apexes of the circumferentially spaced splines. Moreover, accordingto a further feature at least one of the splines is used to help couplethe ablation element to the ablation actuator, such as by allowing anablation actuating member to extend along the spline to an energy sourceof the ablation element, and more specifically by providing fluidcoupling along a passageway along the spline in the case of a fluidablation element, or electrical coupling of electrical conductor leadsalong the spline passageway in the case of an electrical ablationelement.

In another spline variations: the ablation element has a plurality ofindividual ablation elements, each extending along the circumferentialsupport member between two adjacent splines; or, the splines comprises amaterial having a memory to the second configuration, such as by meansof a shape memory material such as a nickel titanium alloy.

Further to other aspects of this mode, the ablation element may be oneor more specific types of ablation elements, such as fluid, electrical,cryo, microwave, thermal, light-emitting, or ultrasound ablationelements.

In one specific variation incorporating the electrical ablation aspectof this mode, at least one electrode is provided along thecircumferential support member that is adapted to be coupled to anelectrical current source. A porous wall substantially surrounds theelectrode within an enclosed fluid chamber that is adapted to be fluidlycoupled to a source of electrically conductive fluid. The porous wall isfurther adapted to electrically couple an ablative electrical currentbetween the circumferential region of tissue positioned coincident tothe circumferential area and the electrode via the electricallyconductive fluid.

According to another mode of the invention, a circumferential ablationmember includes a housing, a mechanical positioning assembly thatadjusts the housing between certain specific first and secondconditions, and an ablation element also cooperating with the housing toablate the circumferential region of tissue. Further to this mode, thehousing is mechanically adjustable between a first condition and asecond condition. In the first condition the distal wall issubstantially radially collapsed such that the housing is adapted to bedelivered through a delivery sheath into the atrium. In the secondcondition the distal wall is radially extended at least in part from thelongitudinal axis with a distal orientation and a distal facing surfacelocated along a circumferential region that surrounds the longitudinalaxis. A mechanical positioning assembly is coupled to the housing tomechanically adjust the housing between the first and second conditions.An ablation element cooperates with the housing and is adapted toablatively couple to a circumferential area normal to the distal facingsurface along the circumferential region when the housing is in thesecond position. The distal facing surface is configured such that thecircumferential area coincides with the circumferential region of tissuewhen the housing is adjusted to the second condition at the location,and therefore the ablation element is adapted to ablate thecircumferential region of tissue in that position.

In one beneficial aspect of this mode, the distal wall in the secondcondition comprises a porous membrane that encloses at least in part afluid chamber within the housing. The distal facing surface is locatedalong the porous membrane, and the porous membrane is adapted toablatively couple a volume of ablative fluid within the fluid chamber tothe circumferential area. In one further regard, the porous membrane isadapted to allow the volume of ablative fluid to flow from within thefluid chamber and into the circumferential area. Still further, theablation element may comprise a volume of ablative fluid medium withinthe fluid chamber and that ablatively couples with the circumferentialarea across the porous membrane. In a still further variation, theporous membrane is constructed at least in part from a poroustetrafluoropolymer. In another variation, the ablation element includesan ablative energy source located within the fluid chamber.

In another more detailed aspect of this mode, the housing has an outerjacket with a distal end portion and a proximal end portion, the distalwall is located along the distal end portion, and a proximal wall islocated along the proximal end portion. The mechanical positioningassembly comprises an array of longitudinal splines that arecircumferentially spaced around the longitudinal axis, wherein each ofthe longitudinal splines has a distal end portion and a proximal endportion and an intermediate region therebetween. The distal and proximalend portions of the outer jacket are positioned to surround at least apart of the proximal and distal end portions of the splines,respectively. According to this relationship, in the first condition theproximal and distal end portions of each spline are respectively spacedalong the longitudinal axis with the intermediate region beingsubstantially radially collapsed within the outer jacket. The housing isadjusted to the second condition by longitudinally collapsing therelative position of the proximal and distal end portions of each splinesuch that the intermediate region of each spline and outer jacketadjacent thereto deflects radially outwardly from the longitudinal axissuch that distal and proximal orientations, respectively, are given tothe distal and proximal walls. In one variation of this aspect, theouter jacket comprises an elastomeric material.

In another aspect of this mode the housing also has a proximal wall thatin the second condition has a proximally facing surface. The proximalwall according to this aspect is connected to the distal wall, such asin a still further variation by being formed from an integral member. Ina still more detailed variation however, the distal and proximal wallsare connected along at least one of (a) an outer circumferential regionthat circumscribes the circumferential region that includes the distalfacing surface, or (b) an inner circumferential region that iscircumscribed by the circumferential region that includes the distalfacing surface. In yet another variation, the mechanical positioningassembly provides at least one support member extending between thedistal and proximal walls at least across an inner circumferentialregion, which is circumscribed by the circumferential region thatincludes the distal facing surface, and the circumferential region withthat distal facing surface.

According to another aspect of the mechanically adjustable ablativehousing mode, the mechanical positioning assembly is coupled to thedelivery member.

In another more detailed aspect of this mode, the mechanical positioningassembly comprises an array of splines that are circumferentially spacedaround the longitudinal axis of the delivery member. Each spline has adistal end portion coupled to the distally oriented wall and a proximalend portion coupled to the distal end portion of the delivery member.Also, each spline is adjustable between a first position that issubstantially radially collapsed and extending along the longitudinalaxis and a second position wherein the distal end portion of the splineextends radially outwardly from the longitudinal axis. Accordingly, thefirst and second positions for the splines characterize at least in partthe first and second conditions for the housing.

Further to this aspect, in one variation the ablation element comprisesan energy source that is located along a spline at a positioncorresponding to the circumferential region.

According to another mode of the invention, a circumferential ablationmember coupled to the distal end portion of a delivery member includesan array of splines supporting an array of individual ablation elementswith each ablation element being supported along a support region of oneof the splines. The splines are circumferentially spaced around thelongitudinal axis. Each spline is adjustable between a first conditionand a second condition, wherein the respectively supported individualablation element is adjustable between a first radial position and asecond radial position. Further to this assembly, each spline issubstantially radially collapsed and extends substantially along thelongitudinal axis in the first condition such that the circumferentialablation member is adapted to be delivered through a delivery sheathinto the atrium. In the second condition, the support region of eachspline extends at least in part radially away from the longitudinalaxis. Each of the individual ablation elements is thus held by thesupporting spline in the second radial position with the array ofindividual ablation elements being spaced along a circumferentialpattern that surrounds the longitudinal axis. This circumferentialpattern is specifically configured such that the array of individualablation elements is adapted to engage and ablate the circumferentialregion of tissue when the splines are adjusted to the second conditionat the location.

In one aspect of this mode, each of the splines has a memory to thesecond condition, such as by being constructed from a shape-memorymaterial that more specifically may be a nickel-titanium alloy.

In another aspect, an outer member surrounds the distal end portion ofthe delivery member. The splines are adapted to be moved in and out ofthe outer member in order to adjust their shape between the first andsecond positions.

According to additional aspects of this mode, the distal end portion ofeach of the splines in the second position may have a radius ofcurvature either away from the longitudinal axis, or in another aspectthe radius of curvature may be toward the longitudinal axis.

According to still further aspects of this mode, the ablation elementmay be one of a number of different types, including one or more of thefollowing: an electrical current ablation element; a thermal ablationelement; an ultrasound ablation element; a microwave ablation element; athermal ablation element; a cryoablation element; a fluid ablationelement; or a light emitting ablation element.

In another mode, the invention provides a contact member in combinationwith a distally oriented ablation element, both being coupled to adelivery member. The contact member is adjustable between a firstcondition for delivery through a delivery sheath into the atrium and asecond condition for circumferential ablation wherein the contact membercomprises a circumferential wall that surrounds the longitudinal axis.The ablation element has an ablative energy source that is located alongthe distal end portion of the delivery member, and cooperates with thecontact member such that the ablative energy source emits acircumferential pattern of energy having a distal orientation throughthe circumferential wall and into a circumferential area normal to thecircumferential wall. Electrical current is not ablatively coupledbetween the ablative energy source and the circumferential areaaccording to this mode. The ablation element and contact member areconfigured such that the circumferential area coincides with thecircumferential region of tissue when the contact member is adjusted tothe second condition at the location.

In one aspect of this mode, the contact member is an inflatable balloonand the ablation element cooperates with the circumferential area asdescribed above through the balloon's outer skin.

According to still further aspects of this mode, the ablation elementmay be one of a number of different types, including one or more of thefollowing: an electrical current ablation element; a thermal ablationelement; an ultrasound ablation element; a microwave ablation element; athermal ablation element; a cryoablation element; a fluid ablationelement; or a light emitting ablation element.

In one variation of the ultrasound ablation element aspect, anultrasound transducer assembly is mounted onto the distal end portionwith a distally oriented face that is adapted to emit an ultrasonicenergy signal distally at an angle relative to the longitudinal axis andthrough the circumferential wall of the contact member. In still afurther more detailed variation, the transducer is conically shaped withan outer conical surface having a distal orientation. In anotherdetailed variation the transducer has a curved distal face.

In still a further detailed variation, the ultrasound transducerassembly has at least one ultrasound transducer panel that is adjustablefrom a radially collapsed position to a radially extended positionhaving a distally oriented face that is adapted to emit thecircumferential pattern of energy with the distal orientation. Furtherto this transducer panel variation, the transducer panel may beadjustable as described by use of an expandable member located betweenthe panel and the distal end portion of the delivery member, whichexpandable member may be a balloon structure or a cage structure.

Other modes, aspects, variations, and features of the invention shallbecome apparent to one of ordinary skill upon review of thisapplication, and in particular by reference to the detailed disclosureof the invention which follows below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 diagrammatically shows sequential, general steps of a method fortreating atrial arrhythmia.

FIGS. 2A–E show schematic, perspective views of various exemplarycircumferential conduction blocks formed at a location where a pulmonaryvein extends from an atrium with a circumferential ablation deviceassembly.

FIG. 3 shows a flow diagram of a method for using a circumferentialablation device assembly to form a circumferential conduction block at alocation where a pulmonary vein extends from an atrium.

FIG. 4 shows a perspective view of a circumferential ablation deviceassembly during use in a left atrium subsequent to performing transeptalaccess and guidewire positioning steps according to the method of FIG.3.

FIG. 5 shows a similar perspective view of the circumferential ablationdevice assembly shown in FIG. 4, and further shows a circumferentialablation catheter during use in ablating a circumferential region oftissue along a pulmonary vein wall to form a circumferential conductionblock in the pulmonary vein according to the method of FIG. 3.

FIG. 6A shows a similar perspective view as shown in FIG. 5, althoughshowing a circumferential ablation catheter which is adapted to allowfor blood perfusion from the pulmonary vein and into the atrium whileperforming the circumferential ablation method shown diagrammatically inFIG. 3.

FIG. 6B is an enlarged partial view of the circumferential ablationcatheter shown in FIG. 6A, with a perfusion lumen shown in phantom.

FIG. 7 shows a similar perspective view of the left atrium as that shownin FIGS. 3–5, although showing a cross-sectional view of acircumferential lesion after being formed by circumferential catheterablation according to the method of FIG. 3.

FIGS. 8A–B show perspective views of another circumferential ablationcatheter during use in a left atrium according to the method of FIG. 3,wherein FIG. 8A shows a radially compliant expandable member with aworking length adjusted to a radially expanded position while in theleft atrium, and FIG. 8B shows the expandable member after advancing itinto and engaging a pulmonary vein ostium while in the radially expandedposition.

FIG. 8C shows the same perspective view of the left atrium shown inFIGS. 8A–B, although shown after forming a circumferential conductionblock according to the circumferential ablation procedure of FIG. 3 andalso after removing the circumferential ablation device assembly fromthe left atrium.

FIG. 8D shows another circumferential ablation catheter during use in aleft atrium, and shows an expandable member in a radially expandedposition which is engaged within a pulmonary vein ostium such that acircumferential band of a circumferential ablation elementcircumscribing the expandable member is also engaged to acircumferential path of tissue along the left posterior atrial wallwhich surrounds the pulmonary vein ostium.

FIG. 8E shows one particular expandable member and circumferentialablation element that is adapted for use according to the mode of useshown in FIG. 8D.

FIG. 8F shows a resulting circumferential conduction block or lesionwhich may be formed with the assemblies shown in FIGS. 8D–E andaccording to the method of use shown in FIG. 8D.

FIG. 9A diagrammatically shows a method for using a circumferentialablation device assembly to form a circumferential conduction block at alocation where a pulmonary vein extends from an atrium in combinationwith a method for forming long linear lesions between pulmonary veinostia in a less-invasive “maze”-type procedure.

FIG. 9B shows a perspective view of a segmented left atrium afterforming several long linear lesions between adjacent pairs of pulmonaryvein ostia according to the method of FIG. 9A.

FIG. 9C shows a similar perspective view as that shown in FIG. 9B,although showing a circumferential ablation device assembly during usein forming a circumferential lesion at a location where a pulmonary veinextends from an atrium which intersects with two linear lesions thatextend into the pulmonary vein, according to the method of FIG. 9A.

FIG. 9D shows a perspective view of another ablation catheter whichcombines a linear ablation member extending between two anchors with acircumferential ablation member for use in forming a circumferentiallesion which intersects with at least one linear lesion according to themethod of FIG. 9A.

FIG. 9E shows a perspective view of another circumferential ablationcatheter for use in forming a circumferential lesion that intersectswith at least one linear lesion according to the method of FIG. 9A.

FIG. 9F shows a perspective view of a segmented left posterior atrialwall with a lesion pattern which results from combining the formation oftwo linear lesions according to FIG. 9B with the formation of acircumferential conduction block according to the methods and devicesshown in FIGS. 8A–C.

FIG. 9G shows a perspective view of a segmented left posterior atrialwall with a lesion pattern which results from combining the formation oftwo linear lesions according to FIG. 9B with the formation of acircumferential conduction block according to the methods and devicesshown in FIGS. 8D–F.

FIG. 9H shows a schematic perspective view of a left posterior atrialwall with one complete lesion pattern in a. variation of a less-invasive“maze”-type procedure wherein circumferential conduction blocks areformed along circumferential paths of tissue along a left posterioratrial wall such that each circumferential conduction block surrounds apulmonary vein ostium, each pair of vertically adjacent circumferentialconduction blocks intersects, and each pair of horizontally adjacentcircumferential conduction blocks are connected with one of two linearlesions extending between the respective pair of horizontally adjacentpulmonary vein ostia.

FIG. 10 diagrammatically shows a further method for using acircumferential ablation device assembly to form a circumferentialconduction block at a location where a pulmonary vein extends from anatrium wall, wherein signal monitoring and “postablation” test elementsare used to locate an arrhythmogenic origin along the pulmonary veinwall and to test the efficacy of a circumferential conduction block inthe wall, respectively.

FIGS. 11A–B show perspective views of one circumferential ablationmember for use in a circumferential ablation device assembly, showing acircumferential ablation electrode circumscribing the working length ofan expandable member with a secondary shape along the longitudinal axisof the working length which is a modified step shape, the expandablemember being shown in a radially collapsed position and also in aradially expanded position, respectively.

FIGS. 11C–D show perspective views of two circumferential ablationelectrodes which form equatorial or otherwise circumferentially placedbands that circumscribe the working length of an expandable member andthat have serpentine and sawtooth secondary shapes, respectively,relative to the longitudinal axis of the expandable member when adjustedto a radially expanded position.

FIGS. 12A–B show perspective views of another circumferential ablationelement which includes a plurality of individual ablation electrodesthat are spaced circumferentially to form an equatorial band whichcircumscribes the working length of an expandable member either in anequatorial location or an otherwise circumferential location that isbounded both proximally and distally by the working length, and whichare adapted to form a continuous circumferential lesion while theworking length is adjusted to a radially expanded position.

FIG. 13 shows a cross-sectional view of another circumferential ablationmember for use in a circumferential ablation device assembly, whereinthe circumferential ablation element circumscribes an outer surface ofan expandable member substantially along its working length and isinsulated at both the proximal and the distal ends of the working lengthto thereby form an uninsulated equatorial band in a middle region of theworking length or otherwise circumferential region of the working lengthwhich is bounded both proximally and distally by end portions of theworking length, which member is adapted to ablate a circumferential pathof tissue in a pulmonary wall adjacent to the equatorial band.

FIG. 14 shows a perspective view of another circumferential ablationmember which is adapted for use in a circumferential ablation deviceassembly, wherein the expandable member is shown to be a cage ofcoordinating wires which are adapted to be adjusted from a radiallycollapsed position to a radially expanded position in order to engageelectrode elements on the wires about a circumferential pattern oftissue at a location where a pulmonary vein extends from an atrium.

FIG. 15 shows a cross-sectional view of another circumferential ablationelement which is adapted for use in a circumferential ablation deviceassembly of the present invention, wherein a superelastic, loopedelectrode element is shown at the distal end of a pusher and is adaptedto circumferentially engage a circumferential region of tissue at alocation where a pulmonary vein extends from an atrium to form acircumferential lesion as a conduction block that circumscribes thepulmonary vein lumen.

FIG. 16A shows a longitudinal perspective view of a circumferentialablation device assembly according to the invention, and shows acircumferential ablation member with an elongated ablation element alongan elongated body which is shown in a first shape having a lineargeometry which is adapted to be delivered through a delivery sheath intoa left atrium.

FIG. 16B shows an exploded longitudinal perspective view of thecircumferential ablation member shown in FIG. 16A, but shows theelongated body after being adjusted to a shape with a looped geometrythat is adapted to engage and ablate a circumferential region of tissue.

FIG. 16C shows a transverse cross-sectional view taken through line16C—16C shown in FIG. 16B.

FIG. 17 shows a longitudinal perspective view of another circumferentialablation device assembly having a circumferential ablation member withan ablation element along an elongated member adjusted to a looped shapein order to ablate a circumferential region of tissue according to theinvention.

FIG. 18 shows a perspective overview of another circumferential ablationdevice assembly having a circumferential ablation member with aplurality of individual ablation elements disposed along splines of abraided cage that is adjusted to a radially expanded condition.

FIG. 19A shows a perspective overview of another circumferentialablation device assembly having a circumferential ablation member with aplurality of individual ablation elements in a first position along aplurality of spline members that are in a radially collapsed conditionwith a longitudinal orientation relative to the shaft of an elongatedcatheter body of the assembly.

FIG. 19B shows a perspective overview of the circumferential ablationdevice assembly shown in 19A, and shows a mid portion of each of theplurality of spline members radially outwardly deflected with theindividual ablation elements in a second position which is adapted toform the circumferential ablation element according to the invention.

FIG. 20A shows a longitudinal side perspective view of anothercircumferential ablation device assembly having a plurality of ablationelements on the distal ends of a plurality of longitudinally orientedspline members extending distally from a delivery sheath and alsoradially with a shape that positions the ablation elements along acircumferential pattern to form a circumferential ablation elementaccording to the invention.

FIG. 20B shows an end view of the circumferential ablation deviceassembly taken along lines 20B—20B shown in FIG. 20A, and shows anablation member having a plurality of individual ablation elements thatform an assembly of bipolar electrodes which are positioned by thespline members along a circumferential pattern having a radius R.

FIG. 20C shows a transverse cross-sectional view taken along line20C—20C of FIG. 20A.

FIGS. 21A–C show side perspective, end, and exploded side perspectiveviews, respectively, of a similar assembly as shown in FIG. 19A,although showing a higher number of ablation elements and associatedspline members that are further shown having a different arcuate shapethan is shown in the FIG. 19A embodiment.

FIG. 22A shows a circumferential ablation device assembly with adelivery sheath and spline combination which is similar to that shown inFIG. 20A, although showing a plurality of elongate ablation elementsextending between the distal ends of the shaped spline members in orderto form a circumferential pattern adapted to ablate a circumferentialregion of tissue according to the invention.

FIG. 22B shows an end view of the assembly taken along line 22B—22Bshown in FIG. 22A.

FIGS. 23A–D show various transverse cross-sectional views of variousparticular embodiments for engaging the spline members within a deliverysheath such as for use according to the assemblies shown in FIGS. 20A,21A, and 22A.

FIG. 24A shows a perspective overview of another circumferentialablation device assembly similar to that shown in FIG. 22A, althoughshowing the circumferential ablation element engaged by and extendingbetween the splines that are radially extended to position thecircumferential ablation element in order to form a circumferentiallesion according to the invention.

FIG. 24B shows a perspective overview of the assembly shown in FIG. 24A,although showing the shaped splines partially coaxially confined withina delivery sheath such that the circumferential ablation element isadjusted to a shape which is adapted for delivery to and from the leftatrium through the delivery sheath.

FIG. 24C shows an exploded perspective view of one embodiment forcoupling a spline member to the circumferentially shaped membersupporting individual ablation elements to form the circumferentialablation member according to a similar assembly such as that shown inFIG. 24A.

FIG. 24D shows an exploded perspective view of another embodiment forthe circumferential ablation element to that shown in FIG. 24C and showsa porous membrane over an arcuate shaped support member that is adaptedto extend between splines FIG. 24E shows an expanded perspective view ofa fluid coupling between a spline member and the porous membrane over anarcuate shaped ablation element.

FIG. 24F shows a perspective view of T-coupling between a spline memberand an arcuate shaped ablation element.

FIGS. 25A–B show a perspective schematic views of anothercircumferential ablation device assembly having a plurality of splinemembers that are rotatably engaged in first and second positions,respectively, relative to a circumferential ablation element accordingto the invention.

FIG. 25C shows a perspective overview of another circumferentialablation device assembly which is similar to that shown in FIGS. 25A–B,but showing spline members that are shaped with a curved geometryadjacent to where they are engaged to the circumferential ablationelement.

FIG. 25D shows a partially shadowed exploded view of a flexible“T”-shaped coupler which couples the spline member and opposing ends oftwo curved ablation elements that form in part the circumferentialablation element, in addition to fluid tubing and porous membersvariously corresponding to those structures.

FIG. 25E shows a partially exploded view of further detail of thecoupling of FIG. 25D, further showing how the fluid tubing and splinemember of that assembly couple proximally with a catheter body forremote delivery and ablation according to the invention.

FIG. 26A shows an end perspective view of another circumferentialablation device assembly which is similar to that shown in FIGS. 22A and24A, although showing spline members having shapes that include complexarcuate looped structures.

FIG. 26B shows a perspective overview of the same assembly shown in FIG.26A and shows the complex, arcuate shaped spline members partiallywithdrawn into a delivery sheath and radially collapsed in asubstantially longitudinal orientation relative to the delivery sheathsuch that the circumferential ablation element is shaped in a partiallycollapsed condition adapted for delivery to and from the left atriumthrough the delivery sheath.

FIG. 26C shows an exploded side view of the same assembly shown in FIG.26B, and shows a portion of the circumferential ablation elementthreaded through a loop of a spline member in order to couple thecircumferential ablation element to the spline member.

FIG. 27A shows an end view of another circumferential ablation deviceassembly having a plurality of shaped splines such as those shown inFIGS. 27A–C, although showing the circumferential ablation elementformed along a circumferential region along a distally disposed surfaceof a forward wall that is supported in the position shown by the splinemembers.

FIG. 27B shows a perspective overview of another circumferentialablation device assembly which is similar to that shown in FIG. 27A,except that the wall is shown to have a different shape around the outerperiphery where it extends radially beyond the supporting splinemembers, and further showing a proximal region of a rear wall of theablation member where it is sealed onto an outer surface of a cathetershaft and also showing a forward wall sealed along the rear wall alongan area which is surrounded by the circumferential region providing thecircumferential ablation element.

FIG. 27C shows an exploded longitudinally cross-sectioned view of acircumferential ablation device assembly which is similar to that shownin FIGS. 27A–B, and shows where the circumferential ablation member iscoupled to the distal end portion of the associated elongated catheterbody for delivering the ablation member into the left atrium.

FIG. 27D shows an exploded cross-sectioned view taken along line 27D—27Dof FIG. 27C and shows the layered structure at the base of thecircumferential ablation member adjacent to the coupling to theelongated catheter body.

FIG. 28A shows a partially longitudinally cross-sectioned view ofanother circumferential ablation member which is similar to that shownin FIGS. 27A–E, except showing a tip region of the catheter bodyextending further distally than that shown in FIG. 27D, and showingradially spaced inner and an outer seal between the forward and rearwardwalls that form a sealed void space along the circumferential region ofthe forward wall along which the circumferential ablation element isformed.

FIG. 28B shows an exploded longitudinally cross-sectioned view of thecircumferential ablation member shown in FIG. 28A where it couples tothe elongated catheter body.

FIG. 28C shows a cross-sectioned view taken along lines 28C—28C of FIG.28A, and shows an area where two adjacent portions of a spline memberare imbedded between the inner seal between the forward and rearwardwalls.

FIG. 28D shows a cross-sectioned view taken along lines 28D—28D of FIG.28A, and shows an area where two adjacent spline members extend alongthe void space along the circumferential region where thecircumferential ablation element is formed.

FIG. 29A shows a cross-sectioned longitudinal view of anothercircumferential ablation device assembly.

FIG. 29B shows an enlarged cross-sectioned view of the distal portion ofthe ablation device assembly of FIG. 29A.

FIG. 30A shows a partially sectioned longitudinal side view of anothercircumferential ablation member for use in a circumferential ablationdevice assembly according to the present invention.

FIG. 30B shows a proximal end perspective view of the circumferentialablation member shown in FIG. 30A, showing the splines in phantom.

FIG. 30C shows a distal end perspective view of the circumferentialablation member shown in FIG. 30A.

FIG. 30D shows a sectioned view of one catheter shaft assembly for usein a circumferential ablation device assembly incorporating thecircumferential ablation member shown in FIGS. 30A–30C, and shows thecooperation of coaxially disposed tubing members in the shaft assemblywhich allow for the circumferential ablation element to be adjustedbetween a radially collapsed position and a radially expanded position.

FIG. 31A shows a longitudinal cross-sectional view of anothercircumferential ablation catheter with an ablation element having asingle cylindrical ultrasound transducer which is positioned along aninner member within an expandable balloon which is further shown in aradially expanded condition.

FIG. 31B shows a transverse cross-sectional view of the circumferentialablation catheter shown in FIG. 31A taken along line 31B—31B shown inFIG. 31A.

FIG. 31C shows a transverse cross-sectional view of the circumferentialablation catheter shown in FIG. 31A taken along line 31C—31C shown inFIG. 31A.

FIG. 31D shows a perspective view of the ultrasonic transducer of FIG.31A in isolation.

FIG. 31E shows a modified version of the ultrasonic transducer of FIG.31D with individually driven sectors.

FIG. 32A shows a perspective view of a similar circumferential ablationcatheter to the catheter shown in FIG. 31A, and shows the distal endportion of the circumferential ablation catheter during one mode of usein forming a circumferential conduction block at a location where apulmonary vein extends from an atrium in the region of its ostium alonga left atrial wall (shown in cross-section in shadow).

FIG. 32B shows a similar perspective and cross-section shadow view of acircumferential ablation catheter and pulmonary vein ostium as thatshown in FIG. 32A, although shows another circumferential ablationcatheter wherein the balloon has a tapered outer diameter.

FIG. 32C shows a similar view to that shown in FIGS. 32A–B, althoughshowing another circumferential ablation catheter wherein the balloonhas a “pear”-shaped outer diameter with a contoured surface along ataper which is adapted to seat in the ostium of a pulmonary vein.

FIG. 32D shows a cross-sectional view of one circumferential conductionblock which may be formed by use of a circumferential ablation cathetersuch as that shown in FIG. 32C.

FIG. 33A shows a cross-sectional view of the distal end portion ofanother circumferential ablation catheter, wherein an outer shield orfilter is provided along the balloon's outer surface in order to form apredetermined shape for the circumferential ablation element created bysonic transmissions from the inner ultrasound transducer.

FIG. 33B shows a similar view as that shown in FIG. 33A, althoughshowing the distal end portion of another circumferential ablationcatheter which includes a heat sink as an equatorial band within thecircumferential path of energy emission from an inner ultrasoundtransducer.

FIG. 34A shows a transverse cross-sectional view of an additionalcircumferential ablation catheter with an ablation element having asingle transducer sector segment which is positioned along an innermember within an expandable balloon which is further shown in a radiallyexpanded condition.

FIG. 34B shows a transverse cross-sectional view of a furthercircumferential ablation catheter with an ablation element having asingle curvilinear section that is mounted so as to position its concavesurface facing in a radially outward direction.

FIG. 35A shows a schematic perspective view of another circumferentialablation member during use in forming a circumferential lesion accordingto the present invention.

FIG. 35B shows one ultrasound transducer that has a shape which isadapted for use in a circumferential ablation member such as that shownin FIG. 35A in order to ablate a circumferential region of tissue.

FIG. 35C shows a schematic perspective view of a circumferentialablation member incorporating the ablation element shown in FIG. 35Bwithin an expandable member.

FIG. 35D shows a longitudinal side view of the circumferential ablationmember shown in FIG. 35C during use in ablating a circumferential regionof tissue in a similar manner as is shown in FIG. 35A.

FIG. 35E shows another ablation element that is adapted to ablate acircumferential region of tissue when used in a circumferential ablationmember such as that shown in FIG. 35A.

FIG. 35F shows a longitudinal side view of a circumferential ablationmember incorporating the ablation element shown in FIG. 35E during usein ablating a circumferential region of tissue.

FIG. 35G shows a longitudinal side view of another circumferentialablation member which is similar to that shown in FIG. 35F, except thatthe shaped ultrasound transducer further includes both a distallyoriented conical face a generally cylindrical portion, and shows thecircumferential ablation member during use in ablating a circumferentialregion of tissue according to the invention.

FIG. 36A shows a schematic perspective view of another ablation elementwhich is adapted to be used in a circumferential ablation member such asshown in FIG. 35A, and shows a plurality of circumferentially spaced,radially adjustable ultrasound panels having an arcuate shape.

FIG. 36B shows a longitudinal side view of the ablation element shown inFIG. 36A.

FIG. 36C shows an end view taken from a rearward perspective of theablation element along line 36C—36C shown in FIG. 36A.

FIG. 37A shows a schematic perspective view of a similar ablationelement as that shown in FIG. 36A, except showing the ultrasound panelshaving generally flat planar shapes.

FIG. 37B shows a longitudinal side view of the ablation element shown inFIG. 37A.

FIG. 37C shows an end view taken along line 37C—37C of FIG. 37B.

FIG. 37D shows an exploded longitudinal cross-sectioned view of oneultrasound panel for use in an ablation element such as those shown inFIGS. 37A–C.

FIGS. 38A–D respectively show various actuating members for adjustingthe ultrasound transducer panels such as those shown in FIGS. 37A–C to aradially extended position relative to an interior support shaft whichis adapted to ablate a circumferential region of tissue according toFIG. 35A.

FIG. 39 shows a schematic longitudinal side view of a circumferentialablation member for use in ablating a circumferential region of tissuesuch as according to FIG. 35A, wherein a tapered distal surface of theinflatable balloon is adapted to deflect the angle of ultrasound energytoward the circumferential region of tissue.

FIG. 40 shows a schematic longitudinal side view of anothercircumferential ablation member for use in ablating a circumferentialregion of tissue such as according to FIG. 35A, wherein deflectingsurfaces along the tapered distal surfaces of the balloon are employedto aim the ultrasound energy toward the circumferential region oftissue.

FIG. 41 shows a schematic longitudinal side view of anothercircumferential ablation member for use in ablating a circumferentialregion of tissue such as according to FIG. 35A, wherein deflectingsurfaces along the proximal taper of the balloon are employed to aim theultrasound energy toward the circumferential region of tissue.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The terms “body space,” including derivatives thereof, is hereinintended to mean any cavity or lumen within the body that is defined atleast in part by a tissue wall. For example, the cardiac chambers, theuterus, the regions of the gastrointestinal tract, and the arterial orvenous vessels are all considered illustrative examples of body spaceswithin the intended meaning.

The term “lumen,” including derivatives thereof, is herein intended tomean any body space which is circumscribed along a length by a tubulartissue wall and which terminates at each of two ends in at least oneopening that communicates externally of the body space. For example, thelarge and small intestines, the vas deferens, the trachea, and thefallopian tubes are all illustrative examples of lumens within theintended meaning. Blood vessels are also herein considered lumens,including regions of the vascular tree between their branch points. Moreparticularly, the pulmonary veins are lumens within the intendedmeaning, including the region of the pulmonary veins between thebranched portions of their ostia along a left ventricle wall, althoughthe wall tissue defining the ostia typically presents uniquely taperedlumenal shapes.

The following disclosure referring to FIGS. 1–15 describe variouscircumferential ablation device assemblies which are adapted to treatpatients with atrial arrhythmia by forming a circumferential conductionblock at a location where a pulmonary vein extends from an atrium whichblocks electrical conduction propagating from cardiac tissue along apulmonary vein wall and into the left atrium. The related method oftreatment is further illustrated in diagrammatically form in the flowdiagram of FIG. 1.

The terms “circumference” or “circumferential”, including derivativesthereof, are herein intended to mean a continuous path or line thatforms an outer border or perimeter that surrounds and thereby defines anenclosed region of space. Such a continuous path starts at one locationalong the outer border or perimeter, and translates along the outerborder or perimeter until it is completed at the original startinglocation to enclose the defined region of space. The related term“circumscribe,” including derivatives thereof, is herein intended tomean to enclose, surround, or encompass a defined region of space.Therefore, according to these defined terms, a continuous line which istraced around a region of space and which starts and ends at the samelocation “circumscribes” the region of space and has a “circumference”which is defined by the distance the line travels as it translates alongthe path circumscribing the space.

Still further, a circumferential path or element may include one or moreof several shapes, and may be, for example, circular, oblong, ovular,elliptical, or otherwise planar enclosures. A circumferential path mayalso be three dimensional, such as, for example, two opposite-facingsemi-circular paths in two different parallel or off-axis planes thatare connected at their ends by line segments bridging between theplanes.

For purpose of further illustration, FIGS. 2A–D therefore show variouscircumferential paths A, B, C, and D, respectively, each translatingalong a portion of a pulmonary vein wall and circumscribing a definedregion of space, shown at a, b, c, and d also respectively, eachcircumscribed region of space being a portion of a pulmonary vein lumen.For still further illustration of the three-dimensional circumferentialcase shown in FIG. 2D, FIG. 2E shows an exploded perspective view ofcircumferential path D as it circumscribes multiplanar portions of thepulmonary vein lumen shown at d′, d″, and d′″, which together make upregion d as shown in FIG. 2D.

The term “transect”, including derivatives thereof, is also hereinintended to mean to divide or separate a region of space into isolatedregions. Thus, each of the regions circumscribed by the circumferentialpaths shown in FIGS. 2A–D transects the respective pulmonary vein,including its lumen and its wall, to the extent that the respectivepulmonary vein is divided into a first longitudinal region located onone side of the transecting region, shown, for example, at region “X” inFIG. 2A, and a second longitudinal region on the other side of thetransecting plane, shown, for example, at region “Y” also in FIG. 2A.

Therefore, a “circumferential conduction block” according to the presentinvention is formed along a region of tissue that follows acircumferential path along the pulmonary vein wall, circumscribing thepulmonary vein lumen and transecting the pulmonary vein relative toelectrical conduction along its longitudinal axis. The transectingcircumferential conduction block therefore isolates electricalconduction between opposite longitudinal portions of the pulmonary wallrelative to the conduction block and along the longitudinal axis.

The terms “ablate” or “ablation,” including derivatives thereof, arehereafter intended to mean the substantial altering of the mechanical,electrical, chemical, or other structural nature of tissue. In thecontext of intracardiac ablation applications shown and described withreference to the variations of the illustrative embodiment below,“ablation” is intended to mean sufficient altering of tissue propertiesto substantially block conduction of electrical signals from or throughthe ablated cardiac tissue.

The term “element” within the context of “ablation element” is hereinintended to mean a discrete element, such as an electrode, or aplurality of discrete elements, such as a plurality of spacedelectrodes, which are positioned so as to collectively ablate a regionof tissue.

Therefore, an “ablation element” according to the defined terms mayinclude a variety of specific structures adapted to ablate a definedregion of tissue. For example, one suitable ablation element for use inthe present invention may be formed, according to the teachings of theembodiments below, from an “energy emitting” type that is adapted toemit energy sufficient to ablate tissue when coupled to and energized byan energy source. Suitable “energy emitting” ablation elements for usein the present invention may therefore include, for example: anelectrode element adapted to couple to a direct current (“DC”) oralternating current (“AC”) current source, such as a radiofrequency(“RF”) current source; an antenna element which is energized by amicrowave energy source; a heating element, such as a metallic elementor other thermal conductor which is energized to emit heat such as byconvective or conductive heat transfer, by resistive heating due tocurrent flow, or by optical heating with light; a light emittingelement, such as a fiber optic element which transmits light sufficientto ablate tissue when coupled to a light source; or an ultrasonicelement such as an ultrasound crystal element which is adapted to emitultrasonic sound waves sufficient to ablate tissue when coupled to asuitable excitation source.

In addition, other elements for altering the nature of tissue may besuitable as “ablation elements” under the present invention when adaptedaccording to the detailed description of the invention below. Forexample, a cryoablation element adapted to sufficiently cool tissue tosubstantially alter the structure thereof may be suitable if adaptedaccording to the teachings of the current invention. Furthermore, afluid delivery element, such as a discrete port or a plurality of portsthat are fluidly coupled to a fluid delivery source, may be adapted toinfuse an ablating fluid, such as a fluid containing alcohol, into thetissue adjacent to the port or ports to substantially alter the natureof that tissue.

The term “anchor” is herein intended to broadly encompass any structurethat functions to secure at least a portion of the disclosed ablationdevice assemblies to a pulmonary vein or pulmonary vein ostium, suchthat the circumferential and/or linear ablation elements are positionedsufficiently close to posterior wall of the left atrium to ablativelyengage the targeted tissue. Examples of suitable anchors within thescope of the present disclosure include, conventional guidewires,guidewires with balloons, deflectable/steerable guidewires, shapedstylets, radially expandable members, inflatable members, etc.

The term “diagnose”, including derivatives thereof, is intended toinclude patients suspected or predicted to have atrial arrhythmia, inaddition to those having specific symptoms or mapped electricalconduction indicative of atrial arrhythmia.

Returning to the inventive method as shown in FIG. 1, a patientdiagnosed with atrial arrhythmia according to diagnosing step (1) istreated with a circumferential conduction block according to treatmentstep (2). In one aspect, a patient diagnosed according to diagnosis step(1) with multiple wavelet arrhythmia originating from multiple regionsalong the atrial wall may also be treated in part by forming thecircumferential conduction block according to treatment step (2),although as an adjunct to forming long linear regions of conductionblock between adjacent pulmonary vein ostia in a less-invasive“maze”-type catheter ablation procedure. More detail regarding thisparticular aspect of the inventive method is provided below withreference to a combination circumferential-long linear lesion ablationdevice that is described below with reference to FIGS. 9A–F.

In another aspect of the method of FIG. 1, a patient diagnosed withfocal arrhythmia originating from an arrhythmogenic origin or focus in apulmonary vein is treated according to this method when thecircumferential conduction block is formed along a circumferential pathof wall tissue that either includes the arrhythmogenic origin or isbetween the origin and the left atrium. In the former case, thearrhythmogenic tissue at the origin is destroyed by the conduction blockas it is formed through that focus. In the latter case, thearrhythmogenic focus may still conduct abnormally, although suchaberrant conduction is prevented from entering and affecting the atrialwall tissue due to the intervening circumferential conduction block.

In still a further aspect of the method shown in FIG. 1, thecircumferential conduction block may be formed in one of several waysaccording to treatment step (2). In one example not shown, thecircumferential conduction block may be formed by a surgical incision orother method to mechanically transect the pulmonary vein, followed bysuturing the transected vein back together. As the circumferentialinjury is naturally repaired, such as through a physiologic scarringresponse common to the “maze” procedure, electrical conduction willgenerally not be restored across the injury site. In another example notshown, a circumferential conduction block of one or more pulmonary veinsmay be performed in an epicardial ablation procedure, wherein anablation element is either placed around the target pulmonary vein or istranslated circumferentially around it while being energized to ablatethe adjacent tissue in an “outside-in” approach. This alternative methodmay be performed during an open chest-type procedure, or may be doneusing other known epicardial access techniques.

FIG. 3 diagrammatically shows the sequential steps of a method for usingthe circumferential ablation device assembly of the present invention informing a circumferential conduction block at a location where apulmonary vein extends from an atrium. The circumferential ablationmethod according to FIG. 3 includes: positioning a circumferentialablation element at an ablation region along the pulmonary veinaccording to a series of detailed steps shown collectively in FIG. 3 aspositioning step (3); and thereafter ablating a continuouscircumferential region of tissue in the PV wall at the ablation regionaccording to ablation step (4).

Further to positioning step (3) according to the method of FIG. 3, adistal tip of a guiding catheter is first positioned within the leftatrium according to a transeptal access method, which is furtherdescribed in more detail as follows. The right venous system is firstaccessed using the “Seldinger” technique, wherein a peripheral vein(such as a femoral vein) is punctured with a needle, the puncture woundis dilated with a dilator to a size sufficient to accommodate anintroducer sheath, and an introducer sheath with at least one hemostaticvalve is seated within the dilated puncture wound while maintainingrelative hemostasis. With the introducer sheath in place, the guidingcatheter or sheath is introduced through the hemostatic valve of theintroducer sheath and is advanced along the peripheral vein, into theregion of the vena cavae, and into the right atrium.

Once in the right atrium, the distal tip of the guiding catheter ispositioned against the fossa ovalis in the intraatrial septal wall. A“Brockenbrough” needle or trocar is then advanced distally through theguide catheter until it punctures the fossa ovalis. A separate dilatormay also be advanced with the needle through the fossa ovalis to preparean access port through the septum for seating the guiding catheter. Theguiding catheter thereafter replaces the needle across the septum and isseated in the left atrium through the fossa ovalis, thereby providingaccess for object devices through its own inner lumen and into the leftatrium.

It is however further contemplated that other left atrial access methodsmay be suitable substitutes for using the circumferential ablationdevice assembly of the present invention. In one alternative variationnot shown, a “retrograde” approach may be used, wherein the guidingcatheter is advanced into the left atrium from the arterial system. Inthis variation, the Seldinger technique is employed to gain vascularaccess into the arterial system, rather than the venous, for example, ata femoral artery. The guiding catheter is advanced retrogradedly throughthe aorta, around the aortic arch, into the ventricle, and then into theleft atrium through the mitral valve.

Subsequent to gaining transeptal access to the left atrium as justdescribed, positioning step (3) according to FIG. 3 next includesadvancing a guidewire into a pulmonary vein, which is done generallythrough the guiding catheter seated in the fossa ovalis. In addition tothe left atrial access guiding catheter, the guidewire according to thisvariation may also be advanced into the pulmonary vein by directing itinto the vein with a second sub-selective delivery catheter (not shown)which is coaxial within the guiding catheter, such as, for example, byusing one of the directional catheters disclosed in U.S. Pat. No.5,575,766 to Swartz. Or, the guidewire may have sufficient stiffness andmaneuverability in the left atrial cavity to unitarily subselect thedesired pulmonary vein distally of the guiding catheter seated at thefossa ovalis.

Suitable guidewire designs for use in the overall circumferentialablation device assembly of the present invention may be selected frompreviously known designs, while generally any suitable choice shouldinclude a shaped, radiopaque distal end portion with a relatively stiff,torquable proximal portion adapted to steer the shaped tip under X-rayvisualization. Guidewires having an outer diameter ranging from 0.010inch to 0.035 inch may be suitable. In cases where the guidewire is usedto bridge the atrium from the guiding catheter at the fossa ovalis, andwhere no other sub-selective guiding catheters are used, guidewireshaving an outer diameter ranging from 0.018 inch to 0.035 inch may berequired. It is believed that guidewires within this size range may berequired to provide sufficient stiffness and maneuverability in order toallow for guidewire control and to prevent undesirable guidewireprolapsing within the relatively open atrial cavity.

Subsequent to gaining pulmonary vein access, positioning step (3) ofFIG. 3 next includes tracking the distal end portion of acircumferential ablation device assembly over the guidewire and into thepulmonary vein, followed by positioning a circumferential ablationelement at an ablation region of the pulmonary vein where thecircumferential conduction block is to be desirably formed.

FIG. 4 further shows a circumferential ablation device assembly 100according to the present invention during use in performing positioningstep (3) and ablation step (4) just described with reference to FIG. 3.Included in the circumferential ablation device assembly 100 are guidingcatheter 101, guidewire 102, and circumferential ablation catheter 103.

More specifically, FIG. 4 shows guiding catheter 101 subsequent toperforming a transeptal access method according to FIG. 3, and alsoshows guidewire 102 subsequent to advancement and positioning within apulmonary vein, also according to step (3) of FIG. 3. FIG. 4 showscircumferential ablation catheter 103 as it tracks coaxially overguidewire 102 with a distal guidewire tracking member, which isspecifically shown only in part at first and second distal guidewireports 142,144 located on the distal end portion 132 of an elongatecatheter body 130. A guidewire lumen (not shown) extends between thefirst and second distal guidewire ports 142,144 and is adapted toslideably receive and track over the guidewire. In the particularvariation of FIG. 4, the second distal guidewire port 142 is located ona distal end portion 132 of the elongate catheter body 130, althoughproximally of first distal guidewire port 142.

As would be apparent to one of ordinary skill, the distal guidewiretracking member shown in FIG. 4 and just described may be slideablycoupled to the guidewire externally of the body in a “backloading”technique after the guidewire is first positioned in the pulmonary vein.Furthermore, there is no need in this guidewire tracking variation for aguidewire lumen in the proximal portions of the elongate catheter body130, which allows for a reduction in the outer diameter of the cathetershaft in that region. Nevertheless, it is further contemplated that adesign which places the second distal guidewire port on the proximal endportion of the elongate catheter body would also be acceptable, as isdescribed below, for example, with reference to the perfusion embodimentof FIGS. 6A–B.

In addition, the inclusion of a guidewire lumen extending within theelongate catheter body between first and second ports, as provided inFIG. 4, should not limit the scope of acceptable guidewire trackingmembers according to the present invention. Other guidewire trackingmembers which form a bore adapted to slideably receive and track over aguidewire are also considered acceptable, such as, for example, thestructure adapted to engage a guidewire as described in U.S. Pat. No.5,505,702 to Arney, the entirety of which is hereby incorporated byreference herein.

While the assemblies and methods shown variously throughout the FIGS.include a guidewire coupled to a guidewire tracking member on thecircumferential ablation catheter, other detailed variations may also besuitable for positioning the circumferential ablation element at theablation region in order to form a circumferential conduction blockthere. For example, an alternative circumferential ablation catheter notshown may include a “fixed-wire”-type of design wherein a guidewire isintegrated into the ablation catheter as one unit. In anotheralternative assembly, the same type of sub-selective sheaths describedabove with reference to U.S. Pat. No. 5,575,766 to Swartz for advancinga guidewire into a pulmonary vein may also be used for advancing acircumferential ablation catheter device across the atrium and into apulmonary vein.

FIG. 4 also shows circumferential ablation catheter 103 with acircumferential ablation element 160 formed on an expandable member 170.The expandable member 170 is shown in FIG. 4 in a radially collapsedposition adapted for percutaneous translumenal delivery into thepulmonary vein according to positioning step (3) of FIG. 3. However,expandable member 170 is also adjustable to a radially expanded positionwhen actuated by an expansion actuator 175, as shown in FIG. 5.Expansion actuator 175 may include, but is not limited to, apressurizable fluid source. According to the expanded state shown inFIG. 5, expandable member 170 includes a working length L relative tothe longitudinal axis of the elongate catheter body which has a largerexpanded outer diameter OD than when in the radially collapsed position.Furthermore, the expanded outer diameter OD is sufficient tocircumferentially engage the ablation region of the pulmonary vein.Therefore, the terms “working length” are herein intended to mean thelength of an expandable member which, when in a radially expandedposition, has an expanded outer diameter that is: (a) greater than theouter diameter of the expandable member when in a radially collapsedposition; and (b) sufficient to engage a body space wall or adjacentablation region surrounding the expandable member, at least on twoopposing internal sides of the body space wall or adjacent ablationregion, with sufficient surface area to anchor the expandable member.

Circumferential ablation member 150 also includes a circumferential band(hatched) on the outer surface of working length L that is coupled to anablation actuator 190 at a proximal end portion of the elongate catheterbody (shown schematically). After expandable member 170 is adjusted tothe radially expanded position and at least a portion of working lengthL circumferentially engages the pulmonary vein wall in the ablationregion, the circumferential band of the circumferential ablation member150 is actuated by ablation actuator 190 to ablate the surroundingcircumferential path of tissue in the pulmonary vein wall, therebyforming a circumferential lesion that circumscribes the pulmonary veinlumen and transects the electrical conductivity of the pulmonary vein toblock conduction in a direction along its longitudinal axis.

FIG. 6A shows another circumferential ablation catheter 203 during usealso according to the method of FIG. 3, wherein a perfusion lumen 260(shown in phantom in FIG. 6B) is formed within the distal end portion132 of elongate catheter body 230. The perfusion lumen 260 in thisexample is formed between a distal perfusion port 242 (FIG. 6B), whichin this example is the first distal guidewire port 242, and proximalperfusion port 244. Proximal perfusion port 244 is formed through thewall of the elongate catheter body 230 and communicates with theguidewire lumen (not shown), which also forms the perfusion lumenbetween the distal and proximal perfusion ports. In the particulardesign shown, after the guidewire has provided for the placement of theablation element into the pulmonary vein, the guidewire is withdrawnproximally of the proximal perfusion port 244 so that the lumen (shownschematically in shadow) between the ports is clear for antegrade bloodflow into the distal perfusion port 242, proximally along the perfusionlumen, out the proximal perfusion port 244 and into the atrium(perfusion flow shown schematically with arrows).

Further to the perfusion design shown in FIGS. 6A–B, guidewire 102 ispositioned in a guidewire lumen which extends the entire length of theelongate catheter body 230 in an “over-the-wire”-type of design, whichfacilitates the proximal withdrawal of the guidewire to allow forperfusion while maintaining the ability to subsequently re-advance theguidewire distally through the first distal guidewire port 242 forcatheter repositioning. In one alternative variation not shown, theguidewire is simply withdrawn and disengaged from the second distalguidewire port, in which case the circumferential ablation catheter mustgenerally be withdrawn from the body in order to re-couple the distalguidewire tracking member with the guidewire.

In another alternative perfusion variation not shown which is amodification of the embodiment of FIG. 6A, a proximal perfusion port isprovided as a separate and distinct port positioned between the seconddistal guidewire port and the expandable member, which allows forproximal withdrawal of the guidewire to clear the guidewire lumen andthereby form a perfusion lumen between the first distal guidewire portand the proximal perfusion port. The guidewire of this alternativevariation, however, remains engaged within the guidewire lumen betweenthe second distal guidewire port and the proximal perfusion port.

Passive perfusion during expansion of the expandable member is believedto minimize stasis and allow the target pulmonary vein to continue inits atrial filling function during the atrial arrhythmia treatmentprocedure. In addition, in cases where the ablation element is adaptedto ablate tissue with heat conduction at the ablation region, asdescribed by reference to more detailed embodiments below, the perfusionfeature according to the variation of FIGS. 6A–B may also provide acooling function in the surrounding region, including in the bloodadjacent to the expandable member.

Moreover, in addition to the specific perfusion structure shown anddescribed by reference to FIGS. 6A–B, it is to be further understoodthat other structural variants which allow for perfusion flow duringexpansion of the expandable element may provide suitable substitutesaccording to one of ordinary skill without departing from the scope ofthe present invention.

FIG. 7 shows pulmonary vein 52 after removing the circumferentialablation device assembly subsequent to forming a circumferential lesion70 around the ablation region of the pulmonary vein wall 53 according tothe use of the circumferential ablation device assembly shown instepwise fashion in FIGS. 3–6. Circumferential lesion 70 is shownlocated along the pulmonary vein adjacent to the pulmonary vein ostium54, and is shown to also be “transmural,” which is herein intended tomean extending completely through the wall, from one side to the other.Also, the circumferential lesion 70 is shown in FIG. 7 to form a“continuous” circumferential band, which is herein intended to meanwithout gaps around the pulmonary vein wall circumference, therebycircumscribing the pulmonary vein lumen.

It is believed, however, that circumferential catheter ablation with acircumferential ablation element according to the present invention mayleave some tissue, either transmurally or along the circumference of thelesion, which is not actually ablated, but which is not substantialenough to allow for the passage of conductive signals. Therefore, theterms “transmural” and “continuous” as just defined are intended to havefunctional limitations, wherein some tissue in the ablation region maybe unablated but there are no functional gaps which allow forsymptomatically arrhythmogenic signals to conduct through the conductionblock and into the atrium from the pulmonary vein.

Moreover, it is believed that the functionally transmural and continuouslesion qualities just described are characteristic of a completedcircumferential conduction block in the pulmonary vein. Such acircumferential conduction block thereby transects the vein, isolatingconduction between the portion of the vein on one longitudinal side ofthe lesion and the portion on the other side. Therefore, any foci oforiginating arrhythmogenic conduction which is opposite the conductionblock from the atrium is prevented by the conduction block fromconducting down into the atrium and atrial arrhythmic affects aretherefore nullified.

FIGS. 8A–B show a further variation of the present invention, wherein acircumferential ablation member 350 includes a radially compliantexpandable member 370 which is adapted to conform to a pulmonary veinostium 54 at least in part by adjusting it to a radially expandedposition while in the left atrium and then advancing it into the ostium.A circumferential ablation element 352 forms a band around expandablemember 370, and is coupled to ablation actuator 190. FIG. 8A showsexpandable member 370 after being adjusted to a radially expandedposition while located in the left atrium 50. FIG. 8B further shows theexpandable member after being advanced into the pulmonary vein 52 untilat least a portion of the expanded working length L of circumferentialablation member, which includes a circumferential ablation element 352,engages the pulmonary vein ostium 54. The tapered distal portion 374 ofthe expandable member is shown conforming to the vein 52, whereas theproximal portion 372 is radially expanded so that the circumferentialablation element 352 ablatively contacts the ostium 54, and in somecases, also a portion of the posterior wall of the atrium. FIG. 8C showsa portion of a circumferential lesion 72 that forms a circumferentialconduction block that encompasses the region of the pulmonary veinostium 54 subsequent to actuating the circumferential ablation elementto form the circumferential lesion.

In addition to conforming to the pulmonary vein ostium, the proximalportion 372 of expandable member is also shown in FIG. 8B to engage acircumferential path of tissue along the left posterior atrial wallwhich surrounds ostium 54. Moreover, circumferential band 352 of thecircumferential ablation member is also thereby adapted to engage thatatrial wall tissue. Therefore, the circumferential conduction blockformed according to the method shown and just described in sequentialsteps by reference to FIGS. 8A–B, as shown in-part in FIG. 8C, includesablating the circumferential path of atrial wall tissue and pulmonaryvein wall which surrounds ostium 54. Accordingly, the entire pulmonaryvein, including the ostium, is thereby electrically isolated from atleast a substantial portion of the left atrial wall which includes theother of the pulmonary vein ostia, as would be apparent to one ofordinary skill according to the sequential method steps shown in FIGS.8A–B and by further reference to the resulting circumferential lesion 72shown in FIG. 8C.

FIGS. 8D–E show another highly beneficial circumferential ablationdevice embodiment and use thereof for electrically isolating pulmonaryvein and ostium from a substantial portion of the left posterior atrialwall. However, unlike the embodiment previously shown and described byreference to FIGS. 8A–C, the FIGS. 8D–E embodiment isolates thepulmonary vein without also ablating tissue along the lumen or lining ofthe pulmonary vein or ostium, as is apparent by reference to theresulting circumferential conduction block 72′ shown in FIG. 8F.

In more detail, FIG. 8D shows a similar device assembly as that shown inFIGS. 8A–B, except that circumferential band 352′ has a geometry(primarily width) and position around the proximal portion 372′ of theexpandable member such that it is adapted to engage only acircumferential path of tissue along the left posterior atrial wallwhich surrounds the pulmonary vein ostium. The tapered distal portion374′ is shown engaging the pulmonary vein 52. In one aspect of thisembodiment, the compliant nature of the expandable member may beself-conforming to the region of the ostium such that thecircumferential band is placed against this atrial wall tissue merely byway of conformability.

In another variation, a “pear-shaped” expandable member or balloon thatincludes a contoured taper may be suitable for use according to the FIG.8D embodiment, as is shown by way of example in FIG. 8E. Such a pearshape may be preformed into the expandable member or balloon, or themember may be adapted to form this shape by way of controlled complianceas it expands, such as for example by the use of composite structureswithin the balloon construction. In any case, according to the“pear-shaped” variation, the circumferential band 352′ of the ablationmember is preferably placed along the surface of the contoured taperwhich is adapted to face the left posterior atrial wall during useaccording to the method illustrated by FIG. 8D. It is furthercontemplated that the ablation element may be further extended oralternatively positioned along other portions of the taper, such as isshown by example in shadow at extended band 352″ in FIG. 8E.Accordingly, the variation shown in FIG. 8E to include extended band352″ may also adapt this particular device embodiment for use in formingcircumferential conduction blocks also along tissue within the pulmonaryvein and ostium, such as according to the method shown in FIGS. 8A–C.

The method of forming a circumferential conduction block along acircumferential path of tissue along a left posterior atrial wall andwhich surrounds a pulmonary vein ostium without ablating the tissue ofthe vein or ostium should not be limited to the particular deviceembodiments just illustrated by reference to FIGS. 8D–F. Other devicevariations may be acceptable substitute for use according to thismethod. In one particular example which is believed to be suitable, a“looped” ablation member such as the embodiment illustrated below byreference to FIG. 15 may be adapted to form a “looped” ablation elementwithin the left atrium and then be advanced against the left posterioratrial wall such that the loop engages the circumferential path oftissue along the atrial wall and which surrounds a vein ostium.Thereafter, the looped ablation element may be actuated to ablate theengaged tissue, such as for further illustration like a branding ironforming the predetermined pattern around the pulmonary vein ostium. Inaddition, other device or method variations may also be suitablesubstitutes according to one of ordinary skill.

FIGS. 9A–D collectively show a circumferential ablation device assemblyaccording to the present invention as it is used to form acircumferential conduction block adjunctively to the formation of longlinear lesions in a less-invasive “maze”-type procedure, as introducedabove for the treatment of multiwavelet reentrant type fibrillationalong the left atrial wall.

More specifically, FIG. 9A diagrammatically shows a summary of steps forperforming a “maze”-type procedure by forming circumferential conductionblocks that intersect with long linear conduction blocks formed betweenthe pulmonary veins. As disclosed in co-pending patent application U.S.Ser. No. 08/853,861 entitled “Tissue Ablation Device and Method of Use”,which is herein incorporated in its entirety by reference thereto, abox-like conduction block surrounding an arrhythmogenic atrial wallregion bounded by the pulmonary veins may be created by forming longlinear lesions 57,58 and 59 between anchors in all pairs of adjacentpulmonary vein ostia, such as is shown in part in steps (5) and (6) ofFIG. 9A. However, it is further believed that, in some particularapplications, such linear lesions may be made sufficiently narrow withrespect to the surface area of the pulmonary vein ostia that they maynot intersect, thereby leaving gaps between them which may presentproarrhythmic pathways for abnormal conduction into and from the box,such as is shown between linear lesions 57 and 58 in FIG. 9B. Therefore,by forming the circumferential conduction block according to step (7) ofFIG. 9A, and as shown by use of circumferential ablation member 450 inFIG. 9C, the linear lesions 57 and 58 are thereby bridged and the gapsare closed.

In a further variation to the specific embodiments shown in FIGS. 9B–C,FIG. 9D shows another circumferential ablation device assembly, whichincludes both circumferential and linear ablation elements 452 and 461,respectively. Circumferential ablation member 450 is shown to include anexpandable member 470 that is adjusted to a radially expanded positionthat is asymmetric to the underlying catheter shaft. Linear ablationmember 460 extends along the elongate catheter body proximally from thecircumferential ablation member 450. When expanded sufficiently toengage the pulmonary vein wall, expandable member 470 provides at leasta portion of an anchor for a first end 462 of linear ablation member460.

A shaped stylet 466 is shown in shadow in FIG. 9D within the elongatecatheter body in the region of the second end 464 of the linear ablationmember 460. Shaped stylet 466 is adapted to push the second end 464 intoan adjacent pulmonary vein ostium such that the linear ablation member460 is adapted to substantially contact the left atrial wall between theadjacent vein ostia to form the linear ablation according to the methodof FIG. 9A. In addition to the use of shaped stylet 466, it is furthercontemplated that a different second anchor may be used adjacent tosecond end 464, such as for example an intermediate guidewire trackingmember adapted to track over a guidewire engaged within the pulmonaryvein, as shown in FIG. 9E at intermediate guidewire tracking member 466′which is engaged over guidewire 467.

Moreover, the method shown schematically in FIG. 9A and also in variousdetail by reference to FIGS. 9B–C provides a specific sequence of stepsfor the purpose of illustration. According to this illustrativesequence, the linear lesions are formed first and then are connectedthereafter with the circumferential conduction block. However, acircumferential conduction block may be formed prior to the formation ofthe linear lesions or conduction blocks, or in any other combination orsub-combination of sequential steps, so long as the resultingcombination of lesions allows for the circumferential block to intersectwith and connect with the linear lesions. In addition, thecircumferential conduction block which connects the linear lesions mayalso include a circumferential path of tissue which surrounds andelectrically isolates the pulmonary vein ostium from the rest of theleft posterior atrial wall, such as for example by considering theembodiments just shown and described by reference to FIGS. 9A–E in viewof the embodiment previously shown and described in relation to FIG. 8Cabove.

In addition to the particular embodiments just shown and described byreference to FIGS. 9A–E, other methods are also contemplated forcombining circumferential and linear conduction blocks device assembliesand uses in order to perform a less-invasive “maze”-type procedure. Forexample, FIG. 9F shows one particular lesion pattern which results bycombining a circumferential conduction block 57, formed according to theprevious embodiments of FIGS. 8A–C, with a pair of linear lesions whichare formed according to the method illustrated by FIG. 9B. In a furtherexample shown in FIG. 9G, another lesion pattern is formed by combiningthe pair of linear lesions of FIG. 9B with a circumferential conductionblock formed according to the embodiments which are previouslyillustrated above by reference to FIGS. 9D–F. While the resulting lesionpatterns of FIGS. 9F and 9G differ slightly as regards the particulargeometry and position of the circumferential conduction block formed,the two variations are also similar in that the circumferentialconduction block includes a circumferential path of atrial wall tissue.When such circumferential conduction blocks are formed between adjacentpulmonary vein ostia, shorter linear lesions are therefore sufficient tobridge the circumferential lesions during the overall “maze”-typeprocedure.

To this end, the invention further contemplates one further variationfor a less-invasive “maze”-type procedure (not shown) wherein multiplecircumferential conduction blocks are formed in atrial wall tissue suchthat each pulmonary vein ostium is surrounded by and is electricallyisolated with one circumferential conduction block. A series of fourlinear lesions may be formed between the various pairs of adjacent ostiaand with just sufficient length to intersect with and bridge thecorresponding adjacent circumferential blocks. A box-like conductionblock is thereby formed by the four circumferential conduction blocksand the four bridging linear lesions. A fifth linear lesion may be alsoformed between at least a portion of the box-like conduction block andanother predetermined location, such as for example the mitral valueannulus.

FIG. 9H shows yet a further variation for forming circumferentialconduction blocks along atrial wall tissue around the pulmonary veinostia during a less invasive “maze”-type procedure. According to thisfurther variation, the circumferential conduction block patterns formedaround each of two adjacent superior and inferior pulmonary vein ostiaare shown in FIG. 9H to intersect, thereby alleviating the need for alinear lesion in order to form a conduction block between the ostia.Furthermore, the distances between the inferior and superior ostia, bothon the right and left side of the posterior atrial wall, are believed tobe significantly shorter than the distances between the two adjacentsuperior or inferior ostia. Therefore, FIG. 9H only shows theoverlapping circumferential conduction blocks as just described to bepositioned vertically between the inferior-superior pairs of adjacentostia, and further shows linear lesions which are used to connect theright and left sided ostia of the superior and inferior pairs. In someinstances these linear lesions will not be required to cure, treat orprevent a particular atrial arrhythmia condition. However, othercombinations of these patterns are further contemplated, such as forexample using only overlapping circumferential conduction blocks betweenall adjacent pairs of ostia in order to form the entire “maze”-type leftatrial pattern.

FIG. 10 diagrammatically shows a further method for using thecircumferential ablation device assembly of the present inventionwherein electrical signals along the pulmonary vein are monitored with asensing element before and after ablation according to steps (8) and(9), respectively. Signals within the pulmonary vein are monitored priorto forming a conduction block, as indicated in step (8) in FIG. 10, inorder to confirm that the pulmonary vein chosen contains anarrhythmogenic origin for atrial arrhythmia. Failure to confirm anarrhythmogenic origin in the pulmonary vein, particularly in the case ofa patient diagnosed with focal arrhythmia, may dictate the need tomonitor signals in another pulmonary vein in order to direct treatmentto the proper location in the heart. In addition, monitoring thepre-ablation signals may be used to indicate the location of thearrhythmogenic origin of the atrial arrhythmia, which information helpsdetermine the best location to form the conduction block. As such, theconduction block may be positioned to include and therefore ablate theactual focal origin of the arrhythmia, or may be positioned between thefocus and the atrium in order to block aberrant conduction from thefocal origin and into the atrial wall.

In addition or in the alternative to monitoring electrical conductionsignals in the pulmonary vein prior to ablation, electrical signalsalong the pulmonary vein wall may also be monitored by the sensingelement subsequent to circumferential ablation, according to step (9) ofthe method of FIG. 10. This monitoring method aids in testing theefficacy of the ablation in forming a complete conduction block againstarrhythmogenic conduction. Arrhythmogenic firing from the identifiedfocus will not be observed during signal monitoring along the pulmonaryvein wall when taken below a continuous circumferential and transmurallesion formation, and thus would characterize a successfulcircumferential conduction block. In contrast, observation of sucharrhythmogenic signals between the lesion and the atrial wallcharacterizes a functionally incomplete or discontinuous circumference(gaps) or depth (transmurality) that would potentially identify the needfor a subsequent follow-up procedure, such as a second circumferentiallesioning procedure in the ablation region.

A test electrode may also be used in a “post ablation” signal monitoringmethod according to step (10) of FIG. 10. In one particular embodimentnot shown, the test electrode is positioned on the distal end portion ofan elongate catheter body and is electrically coupled to a currentsource for firing a test signal into the tissue surrounding the testelectrode when it is placed distally or “upstream” of thecircumferential lesion in an attempt to simulate a focal arrhythmia.This test signal generally challenges the robustness of thecircumferential lesion in preventing atrial arrhythmia from any suchfuture physiologically generated aberrant activity along the suspectvein.

Further to the signal monitoring and test stimulus methods justdescribed, such methods may be performed with a separate electrode orelectrode pair located on the catheter distal end portion adjacent tothe region of the circumferential ablation element, or may be performedusing one or more electrodes which form the circumferential ablationelement itself, as will be further developed below.

The designs for the expandable member and circumferential ablationelement for use in a circumferential ablation device assembly as hereindescribed have been described generically with reference to theembodiments shown in the previous FIGS. Examples of various specificexpandable member and ablation element structures that are adapted foruse in such assemblies and methods are further provided as follows.

Notwithstanding their somewhat schematic detail, the circumferentialablation members shown in the previous FIGS. do illustrate oneparticular embodiment wherein a circumferential electrode elementcircumscribes an outer surface of an expandable member. The expandablemember of the embodiments shown may take one of several different forms,although the expandable member is generally herein shown as aninflatable balloon that is coupled to an expansion actuator which is apressurizeable fluid source. The balloon is preferably made of apolymeric material and forms a fluid chamber that communicates with afluid passageway (not shown in the FIGS.) that extends proximally alongthe elongate catheter body and terminates proximally in a proximal fluidport that is adapted to couple to the pressurizeable fluid source.

In one expandable balloon variation, the balloon is constructed of arelatively inelastic polymer such as a polyethylene (“PE”; preferablylinear low density or high density or blends thereof), polyolefincopolymer (“POC”), polyethylene terepthalate (“PET”), polyimide, or anylon material. In this construction, the balloon has a low radial yieldor compliance over a working range of pressures and may be folded into apredetermined configuration when deflated in order to facilitateintroduction of the balloon into the desired ablation location via knownpercutaneous catheterization techniques. In this variation, one balloonsize may not suitably engage all pulmonary vein walls for performing thecircumferential ablation methods of the present invention on all needypatients. Therefore, it is further contemplated that a kit of multipleablation catheters, with each balloon working length having a uniquepredetermined expanded diameter, may be provided from which a treatingphysician may chose a particular device to meet a particular patient'spulmonary vein anatomy.

In an alternative expandable balloon variation, the balloon isconstructed of a relatively compliant, elastomeric material, such as,for example (but not limited to), a silicone, latex, polyurethane, ormylar elastomer. In this construction, the balloon takes the form of atubular member in the deflated, non-expanded state. When the elastictubular balloon is pressurized with fluid such as in the previous,relatively non-compliant example, the material forming the wall of thetubular member elastically deforms and stretches radially to apredetermined diameter for a given inflation pressure. It is furthercontemplated that the compliant balloon may be constructed as acomposite, such as, for example, a latex or silicone balloon skin whichincludes fibers, such as metal, Kevlar, or nylon fibers, which areembedded into the skin. Such fibers, when provided in a predeterminedpattern such as a mesh or braid, may provide a controlled compliancealong a preferred axis, preferably limiting longitudinal compliance ofthe expandable member while allowing for radial compliance.

It is believed that, among other features, the relatively compliantvariation may provide a wide range of working diameters, which may allowfor a wide variety of patients, or of vessels within a single patient,to be treated with just one or a few devices. Furthermore, this range ofdiameters is achievable over a relatively low range of pressures, whichis believed to diminish a potentially traumatic vessel response that mayotherwise be presented concomitant with inflation at higher pressures,particularly when the inflated balloon is oversized to the vessel. Inaddition, the low-pressure inflation feature of this variation issuitable for the present invention because the functional requirement ofthe expandable balloon is merely to engage the ablation element againsta circumferential path along the inner lining of the pulmonary veinwall.

Moreover, a circumferential ablation member is adapted to conform to thegeometry of the pulmonary vein ostium, at least in part by providingsubstantial compliance to the expandable member, as was shown anddescribed previously by reference to FIGS. 8A–B. Further to thisconformability to pulmonary vein ostia as provided in the specificdesign of FIGS. 8A–B, the working length L of expandable member is alsoshown to include a taper which has a distally reducing outer diameterfrom a proximal end to a distal end. In either a compliant or thenon-compliant balloon, such a distally reducing tapered geometry adaptsthe circumferential ablation element to conform to the funnelinggeometry of the pulmonary veins in the region of their ostia in order tofacilitate the formation of a circumferential conduction block there.

Further to the circumferential electrode element embodiment as shownvariously throughout the previous illustrative FIGS., thecircumferential electrode element is coupled to an ablation actuator190. Ablation actuator 190 generally includes a radio-frequency (“RF”)current source (not shown) that is coupled to both the RF electrodeelement and also a ground patch 195 that is in skin contact with thepatient to complete an RF circuit. In addition, ablation actuator 190preferably includes a monitoring circuit (not shown) and a controlcircuit (not shown) which together use either the electrical parametersof the RF circuit or tissue parameters such as temperature in a feedbackcontrol loop to drive current through the electrode element duringablation. Also, where a plurality of ablation elements or electrodes inone ablation element are used, a switching means may be used tomultiplex the RF current source between the various elements orelectrodes.

FIGS. 11A–D show various patterns of electrically conductive,circumferential electrode bands as electrode ablation elements, eachcircumscribing an outer surface of the working length of an expandablemember. FIGS. 11A–B show circumferential ablation member 550 to includea continuous circumferential electrode band 552 that circumscribes anouter surface of an expandable member 570. FIG. 11B more specificallyshows expandable member 570 as a balloon which is fluidly coupled to apressurizeable fluid source 175, and further shows electrode band(circumferential ablation element) 552 electrically coupled viaelectrically conductive lead 554 to ablation actuator 190. In addition,a plurality of apertures 572 are shown in the balloon skin wall ofexpandable member 570 adjacent to electrode band 552. The purpose ofthese apertures 572 is to provide a positive flow of fluid such assaline or ringers lactate fluid into the tissue surrounding theelectrode band 552. Such fluid flow is believed to reduce thetemperature rise in the tissue surrounding the electrode element duringRF ablation.

The shapes shown collectively in FIGS. 11A–D allow for a continuouselectrode band to circumscribe an expandable member's working lengthover a range of expanded diameters, a feature which is believed to beparticularly useful with a relatively compliant balloon as theexpandable member. In the particular embodiments of FIGS. 11A–D, thisfeature is provided primarily by a secondary shape given to theelectrode band relative to the longitudinal axis of the working lengthof the expandable member. Electrode band 552 is thus shown in FIGS.11A–B to take the specific secondary shape of a modified step curve.Other shapes than a modified step curve are also suitable, such as theserpentine or sawtooth secondary shapes shown respectively in FIGS.11C–D. Other shapes in addition to those shown in FIGS. 11A–D and whichmeet the defined functional requirements are further contemplated withinthe scope of the present invention.

In addition, the electrode band provided by the circumferential ablationelements shown in FIGS. 11C–D and also shown schematically in FIGS. 3–6Bhas a functional band width w relative to the longitudinal axis of theworking length which is only required to be sufficiently wide to form acomplete conduction block against conduction along the walls of thepulmonary vein in directions parallel to the longitudinal axis. Incontrast, the working length L of the respective expandable element isadapted to securely anchor the distal end portion in place such that theablation element is firmly positioned at a selected region of thepulmonary vein for ablation. Accordingly, the band width w is relativelynarrow compared to the working length L of the expandable element, andthe electrode band may thus form a relatively narrow equatorial bandwhich has a band width that is less than two-thirds or even one-half ofthe working length of the expandable element. Additionally, it is to benoted here and elsewhere throughout the specification, that a narrowband may be placed at locations other than the equator of the expandableelement, preferably as long as the band is bordered on both sides by aportion of the working length L.

In another aspect of the narrow equatorial band variation for thecircumferential ablation element, the circumferential lesion formed mayalso be relatively narrow when compared to its own circumference, andmay be less than two-thirds or even one-half its own circumference onthe expandable element when expanded. In one arrangement, which isbelieved to be suitable for ablating circumferential lesions in thepulmonary veins as conduction blocks, the band width w is less than 1 cmwith a circumference on the working length when expanded that is greaterthan 1.5 cm.

FIGS. 12A–B show a further variation of a circumferential ablationelement which is adapted to maintain a continuous circumferential lesionpattern over a range of expanded diameters and which includes electrodeelements that form a relatively narrow equatorial band around theworking length of an expandable balloon member. In this variation, aplurality of individual electrode/ablation elements 562 are included inthe circumferential ablation element and are positioned in spacedarrangement along an equatorial band which circumscribes an outersurface of the expandable member's working length L.

The size and spacing between these individual electrode elements 562,when the balloon is expanded, is adapted to form a substantiallycontinuous circumferential lesion at a location where a pulmonary veinextends from an atrium when in intimal contact adjacent thereto, and isfurther adapted to form such a lesion over a range of band diameters asthe working length is adjusted between a variety of radially expandedpositions. Each individual electrode element 562 has two opposite ends563,564, respectively, along a long axis LA and also has a short axisSA, and is positioned such that the long axis LA is at an acute anglerelative to the longitudinal axis La of the elongate catheter body andexpandable member 560. At least one of the ends 563,564 along the longaxis LA overlaps with an end of another adjacent individual electrodeelement, such that there is a region of overlap along theircircumferential aspect, i.e., there is a region of overlap along thecircumferential coordinates. The terms “region of overlap along theircircumferential coordinate” are herein intended to mean that the twoadjacent ends each are positioned along the working length with acircumferential and also a longitudinal coordinate, wherein they share acommon circumferential coordinate. In this arrangement, thecircumferential compliance along the working length, which accompaniesradial expansion of the expandable member, also moves the individualelectrode elements apart along the circumferential axis. However, thespaced, overlapping arrangement described allows the individual ablationelements to maintain a certain degree of their circumferential overlap,or at least remain close enough together, such that a continuous lesionmay be formed without gaps between the elements.

The construction for suitable circumferential electrode elements in theRF variation of the present invention, such as the various electrodeembodiments described with reference to FIGS. 11A–12B, may comprise ametallic material deposited on the outer surface of the working lengthusing conventional techniques, such as by plasma depositing, sputtercoating, chemical vapor deposition, other known techniques which areequivalent for this purpose, or otherwise affixing a metallic shapedmember onto the outer surface of the expandable member such as throughknown adhesive bonding techniques. Other RF electrode arrangements arealso considered within the scope of the present invention, so long asthey form a circumferential conduction block as previously described.For example, a balloon skin may itself be metallized, such as by mixingconductive metal, including but not limited to gold, platinum, orsilver, with a polymer to form a compounded, conductive matrix as theballoon skin.

Still further to the RF electrode embodiments, another circumferentialablation member variation (not shown) may also include an expandablemember, such as an inflatable balloon, that includes a porous skin thatis adapted to allow fluid, such as hypertonic saline solution, to passfrom an internal chamber defined by the skin and outwardly intosurrounding tissues. Such a porous skin may be constructed according toseveral different methods, such as by forming holes in an otherwisecontiguous polymeric material, including mechanically drilling or usinglaser energy, or the porous skin may simply be an inherently porousmembrane. In any case, by electrically coupling the fluid within theporous balloon skin to an RF current source (preferably monopolar), theporous region of the expandable member serves as an RF electrode whereinRF current flows outwardly through the pores via the conductive fluid.In addition, it is further contemplated that a porous outer skin may beprovided externally of another, separate expandable member, such as aseparate expandable balloon, wherein the conductive fluid is containedin a region between the porous outer skin and the expandable membercontained therein. Various other “fluid electrode” designs than thosespecifically herein described may also be suitable according to one ofordinary skill upon review of this disclosure.

In the alternative, or in addition to the RF electrode variations justdescribed, the circumferential ablation element may also include otherablative energy sources or sinks, and particularly may include a thermalconductor that circumscribes the outer circumference of the workinglength of an expandable member. Examples of suitable thermal conductorarrangements include a metallic element that may, for example, beconstructed as previously described for the more detailed RF embodimentsabove. However, in the thermal conductor embodiment such a metallicelement would be generally either resistively heated in a closed loopcircuit internal to the catheter, or conductively heated by a heatsource coupled to the thermal conductor. In the latter case ofconductive heating of the thermal conductor with a heat source, theexpandable member may be, for example, a polymeric balloon skin that isinflated with a fluid that is heated either by a resistive coil or bybipolar RF current. In any case, it is believed that a thermal conductoron the outer surface of the expandable member is suitable when it isadapted to heat tissue adjacent thereto to a temperature between 40° and80° C.

Further to the thermal conduction variation for the circumferentialablation element, the perfusion balloon embodiment as shown in FIGS.6A–B may be particularly useful in such a design. It is believed thatablation through increased temperatures, as provided by example abovemay also enhance coagulation of blood in the pulmonary vein adjacent tothe expandable member, which blood would otherwise remain stagnantwithout such a perfusion feature.

One further circumferential ablation element design that is believed tobe highly useful in performing the methods according to the presentinvention is shown in FIG. 13 to include a circumferential ablationmember 600 with two insulators 602,604 that encapsulate the proximal anddistal ends, respectively, of the working length L of an expandablemember 610. In the particular embodiment shown, the insulators 602,604are thermal insulators, such as a thermal insulator comprising a Teflonmaterial. Expandable member 610 is an inflatable balloon which has aballoon skin 612 that is thermally conductive to surrounding tissue wheninflated with a heated fluid that may contain a radiopaque agent, salinefluid, ringers lactate, combinations thereof, and/or other knownbiocompatible fluids having acceptable heat transfer properties forthese purposes. By providing these spaced insulators, a circumferentialablation element is formed as an equatorial band 603 of uninsulatedballoon skin located between the opposite insulators. In thisconfiguration, the circumferential ablation element is able to conductheat externally of the balloon skin much more efficiently at theuninsulated equatorial band 603 than at the insulated portions, andthereby is adapted to ablate only a circumferential region of tissue ina pulmonary vein wall that is adjacent to the equatorial band. It isfurther noted that this embodiment is not limited to an “equatorial”placement of the ablation element. Rather, a circumferential band may beformed anywhere along the working length of the expandable member andcircumscribing the longitudinal axis of the expandable member aspreviously described.

FIG. 13 further shows use of a radiopaque marker 620 to identify thelocation of the equatorial band 603 in order to facilitate placement ofthat band at a selected ablation region of a pulmonary vein via X-rayvisualization. Radiopaque marker 620 is opaque under X-ray, and may beconstructed, for example, of a radiopaque metal such as gold, platinum,or tungsten, or may comprise a radiopaque polymer such as a metal loadedpolymer. FIG. 13 shows radiopaque marker 620 positioned coaxially overan inner tubular member 621 that is included in a coaxial catheterdesign as would be apparent to one of ordinary skill. Such a radiopaquemarker may also be combined with the other embodiments herein shown anddescribed. When the circumferential ablation member that forms anequatorial band includes a metallic electrode element, such electrodemay itself be radiopaque and may not require use of a separate marker asjust described.

The thermal insulator embodiment just described by reference to FIG. 13is illustrative of a broader embodiment, wherein a circumferentialablation member has an ablating surface along the entire working lengthof an expandable member, but is shielded from releasing ablative energyinto surrounding tissues except for along an unshielded or uninsulatedequatorial band. As such, the insulator embodiment contemplates otherablation elements, such as the RF embodiments previously describedabove, which are provided along the entire working length of anexpandable member and which are insulated at their ends to selectivelyablate tissue only about an uninsulated equatorial band.

In a further example using the insulator embodiment in combination witha circumferential RF electrode embodiment, a metallized balloon, whichincludes a conductive balloon skin, may have an electrical insulator,such as a polymeric coating, at each end of the working length andthereby selectively ablate tissue with electricity flowing through theuninsulated equatorial band. In this and other insulator embodiments, itis further contemplated that the insulators described may be onlypartial and still provide the equatorial band result. For instance, inthe conductive RF electrode balloon case, a partial electrical insulatorwill allow a substantial component of current to flow through theuninsulated portion due to a “shorting” response to the lower resistancein that region.

In still a further example of an insulator combined with a RF ablationelectrode, a porous membrane comprises the entire balloon skin of anexpandable member. By insulating the proximal and distal end portions ofthe working length of the expandable member, only the pores in theunexposed equatorial band region are allowed to effuse the electrolytethat carries an ablative RF current.

Further to the expandable member design for use in a circumferentialablation element according to the present invention, other expandablemembers than a balloon are also considered suitable. For example, in oneexpandable cage embodiment shown in FIG. 14, cage 650 comprisescoordinating wires 651 and is expandable to engage a desired ablationregion at a location where a pulmonary vein extends from an atrium.

The radial expansion of cage 650 is accomplished as follows. Sheath 652is secured around the wires proximally of cage 650. However, core 653,which may be a metallic mandrel such as stainless steel, extends throughsheath 652 and distally within cage 650 wherein it terminates in adistal tip 656. Wires 651 are secured to distal tip 656, for example, bysoldering, welding, adhesive bonding, heat shrinking a polymeric memberover the wires, or any combination of these methods. Core 653 isslideable within sheath 652, and may, for example, be housed within atubular lumen (not shown) within sheath 652, the wires being housedbetween a coaxial space between the tubular lumen and sheath 652. Bymoving the sheath 652 relative to core 653 and distal tip 656 (shown byarrows in FIG. 14), the cage 650 is collapsible along its longitudinalaxis in order to force an outward radial bias (also shown with arrows inFIG. 14) to wires 651 in an organized fashion to formed a working lengthof cage 650 which is expanded (not shown).

Further to the particular expandable cage embodiment shown in FIG. 14, aplurality of ablation electrodes 655 is shown, each being positioned onone of wires 651 and being similarly located along the longitudinal axisof the cage 650. The radial bias given to wires 651 during expansion,together with the location of the ablation electrodes 655, serves toposition the plurality of ablation electrodes/elements 655 along acircumferential, equatorial band along the expanded working length ofcage 650. The wires forming a cage according to this embodiment may alsohave another predetermined shape when in the radially expanded position.For example, a taper similar to that shown for expandable member 370 inFIG. 8A may be formed by expanding cage 650, wherein the ablationelement formed by ablation electrodes 655 may be positioned between theproximal end and the distal end of the taper.

Further to the construction of the embodiment shown in FIG. 14, wires651 are preferably metal, and may comprise stainless steel or asuperelastic metal alloy, such as an alloy of nickel and titanium, or acombination of both. Regarding the case of nickel and titaniumconstruction for the wires 655, a separate electrical conductor may berequired in order to actuate ablation electrodes 655 to efficiently emitablative current into surrounding tissues. In the case where wires 651are constructed of stainless steel, they may also serve as electricalconductors for ablation electrodes 655. Further to the stainless steeldesign, the wires 651 may be coated with an electrical insulator toisolate the electrical flow into surrounding tissues at the site of theablation electrodes 655. Moreover, the ablation electrodes 655 in thestainless steel wire variation may be formed simply by removingelectrical insulation in an isolated region to allow for current to flowinto tissue only from that exposed region.

In a further cage embodiment (not shown) to that shown in FIG. 14, acircumferential strip of electrodes may also be secured to the cage suchthat the strip circumscribes the cage at a predetermined location alongthe cage's longitudinal axis. By expanding cage as previously described,the strip of electrodes are adapted to take a circumferential shapeaccording to the shape of the expanded cage. Such an electrode strip ispreferably flexible, such that it may be easily reconfigured when thecage is adjusted between the radially collapsed and expanded positionsand such that the strip may be easily advanced and withdrawn with thecage within the delivery sheath. Furthermore, the electrode strip may bea continuous circumferential electrode such as a conductive spring coil,or may be a flexible strip that includes several separate electrodesalong its circumferential length. In the latter case, the flexible stripmay electrically couple all of the electrodes to a conductive lead thatinterfaces with a drive circuit, or each electrode may be separatelycoupled to one or more such conductive leads.

Another circumferential ablation element adapted for use in thecircumferential conduction block assembly according to the presentinvention is shown in FIG. 15, wherein circumferential ablation member700 includes a looped member 710 attached, preferably by heat shrinking,to a distal end of a pusher 730. Looped member 710 and pusher 730 areslideably engaged within delivery sheath 750 such that looped member 710is in a first collapsed position when positioned and radially confinedwithin delivery sheath 750, and expands to a second expanded positionwhen advanced distally from delivery sheath 750.

Looped member 710 is shown in more detail in FIG. 15 to include a core712 which is constructed of a superelastic metal alloy such as anickel-titanium alloy and which has a looped portion with shape memoryin the looped configuration. This looped configuration is shown in FIG.15 to be in a plane that is off-axis, preferably perpendicular, to thelongitudinal axis of the pusher 730. This off-axis orientation of theloop is adapted to engage a circumferential path of tissue along apulmonary vein wall that circumscribes the pulmonary vein lumen when thelooped member 710 is delivered from the delivery sheath 750 when thedelivery sheath is positioned within the vein lumen parallel to itslongitudinal axis. An ablation electrode 714 is also shown in FIG. 15 asa metallic coil that is wrapped around core 712 in its looped portion.

Pusher 730 is further shown in FIG. 15 to include a tubular pushermember 732 that is heat shrunk over two ends 712′ of core 712 whichextend proximally of looped member 710 through pusher 730 in theparticular variation shown. While in this embodiment, core 712 extendsthrough the pusher in order to provide stiffness to the composite designfor the pusher. It is further contemplated that the superelastic metalof the core may be replaced or augmented in the pusher region withanother different mandrel or pusher core (not shown), such as a stifferstainless steel mandrel. Also shown within pusher 730 is an electricallyconductive lead 735 which is coupled to the ablation electrode 714 andwhich is also adapted in a proximal region of the pusher (not shown) tocouple to an ablation actuator 190 such as an RF current source (shownschematically).

The embodiments shown and described with reference to FIGS. 16–31 beloware believed to provide assemblies that are particularly well adaptedfor ablating a circumferential region of tissue along the posterior leftatrial wall that surrounds a pulmonary vein ostium and isolates thesurrounded tissue including the pulmonary vein from the rest of the leftatrium in order to prevent atrial fibrillation.

According to the circumferential ablation device assembly 1600 shown inFIGS. 16A–C, a plurality of electrodes 1630 are spaced along elongatedmember 1625, which is disposed on the distal end portion of catheterbody 1610. Elongated member 1625 is adjustable between a first shape(shown in FIG. 16A), which substantially extends along the longitudinalaxis L of catheter body 1610, and a second shape (FIG. 16B), which has alooped geometry about a circumference substantially along a plane thatis orthogonal to the longitudinal axis L. The first shape is adapted fordelivery through a delivery sheath and into the left atrium. The secondshape is adapted to position the ablation elements about a circumferencein order to form the circumferential ablation element for ablating acircumferential region of tissue where a pulmonary vein extends from aleft atrium.

More specifically, an actuating assembly incorporating pull wire 1667 isused to adjust the elongated member 1625 between shapes. Pull wire 1627is secured to tip 1626 distally of elongated member 1625 and extendsproximally along the side of elongated member 1625 and further throughport 1618 where it is slideably engaged within a passageway (not shown)along catheter body 1610, terminating along the proximal end portion ofcatheter body 1610, where it may be manipulated. Because the distal end1626 of elongated member 1625 is also secured to tip 1619, pulling pullwire 1627 relative to catheter body 1610 longitudinally collapses distalend 1626 toward proximal end 1624 along pull wire 1627 and therebydeflects elongated member 1625 radially outwardly from the catheterassembly. By pre-forming a bias onto elongated member, the elongatedmember 1625 forms a loop along a plane that is orthogonal to thelongitudinal axis of the catheter body 1610, as shown in FIGS. 16B–C.

Moreover, the assembly 1600 is further shown to be adapted to track overa guidewire 1602 via a guidewire lumen 1615 that is shown in FIGS. 16A–Cto extend along elongated member 1625 and further proximally alongcatheter body 1610. As such, elongated member 1625 is preferablypositioned over a sufficiently flexible portion of the guidewire inorder to form the looped shape as just described. Moreover, it isfurther contemplated that distal and proximal guidewire tracking membersor bores (not shown) may be provided on distal tip 1619 and catheterbody 1610, respectively, such that the guidewire 1602 may also extendalong the outside of elongated member 1625 and pull wire 1627, such thatthe elongate member's shape when deflected is not affected by guidewire1602. Further to this dual tracking member embodiment, a stop (notshown) may be provided on guidewire 1602 distally of distal tip 1619such that pull wire 1627 is no longer necessary to adjust the shapes ofelongated body 1610. In this embodiment, by advancing distal tip 1619against a stop, the proximal and distal ends 1624,1626 of elongatedmember 1625 are longitudinally collapsed together along guidewire 1602to provide the desired deflection for elongated member 1625.

Circumferential ablation device assembly 1700 shown in FIG. 17 alsoincludes a plurality of individual ablation elements 1730 along anelongated member 1725 that is adjusted to a looped shape in order toposition individual elements 1730 about a circumference to form thecircumferential ablation element 1731 according to the invention.However, according to the FIG. 17 embodiment, elongate member 1725 isprovided along a distal end portion of a pushing member (not shown) thatis slideably engaged within a passageway 1717 extending proximally alongcatheter body 1710. In addition, a distal member 1712 extends distallyfrom catheter body 1710 and beyond the circumferential ablation member1720 in order to track over guidewire 1702 slideably engaged inguidewire passageway 1715 and anchor distally within the pulmonary veinwhile circumferential ablation member 1720 engages and ablates acircumferential region of tissue where the vein extends from the atrialwall, and in particular along the atrial wall and surrounding the veinostium. A balloon 1716 is also shown in FIG. 17 in shadow in order toassist in such anchoring by securing distal member 1712 in a desiredposition distally within the vein. The looped shape for elongate member1725 is further shown to encircle distal member 1712 and desirably thedistal tip 1726 of elongate member 1725 terminates in the looped shapenear a proximal portion 1724 of elongate member 1725 in order tofacilitate formation of complete and continuous circumferential lesions.It is further contemplated that the distal end portion of elongatemember 1725, such as the tip 1726, may be secured to distal member 1712in order to facilitate adjusting elongate member 1725 to a repeatablelooped shape during use. According to one aspect of the FIG. 17embodiment as just described, catheter 1701 may be secured in position,such as by inflating a balloon 1716 within a pulmonary vein, whilecircumferential ablation member 1720 is advanced distally and adjustedas desired relative to the catheter in order to form the desired lesion.

Circumferential ablation device assembly 1800 shown in FIG. 18 providesa plurality of individual ablation elements, similar to the wire cageillustrated and described with reference to FIG. 14. The individualablation elements (not shown) are disposed along splines of a braidedcage in order to form a circumferential ablation member 1820 accordingto the invention. Braided cage 1825 is adjustable between radiallycollapsed and expanded conditions by longitudinally collapsing distaland proximal ends 1824,1826 such as previously described above.Moreover, braided cage 1825 may be further adapted such that apronounced “forward-looking” circumferential wall 1826 is formed alongone region of the braid. By providing the ablation elements in acircumferential pattern along that region, a circumferential ablationelement is formed for advancing against tissue for ablation, such asagainst a posterior left atrial wall to ablate around a pulmonary veinostium. One such shape incorporating a forward-looking face of thebraided cage is shown for the purpose of illustration in shadow in FIG.18. In one aspect of this embodiment, the pitch, pattern, or physicalquality of the splines in the braided network may be varied in order toselectively control the shape of different regions of the braid as itsends are longitudinally collapsed.

It is further contemplated that braided cages such as the types justdescribed may be also used in combination with an inner or outer wall,such as a flexible polymeric wall, in order to expand an enclosedstructure into a desired shape for ablation. Such a composite expandablemember provides a suitable substitute to the inflatable balloon ablationembodiments herein shown and described.

Circumferential ablation device assembly 1900 shown in FIG. 19A forms acircumferential ablation element by providing a plurality of individualablation elements along a plurality of radially adjustable splinemembers 1925 that are formed between longitudinal grooves that are cutalong a tubular wall 1911 extending at least in part along the distalend portion of catheter body 1910. A distal end 1913 of tubular wall1911 is secured to an inner member 1912 that extends proximally of thespline members and within a passageway extending to the proximal endportion of catheter body 1910. By advancing tubular wall 1911 distallywith respect to inner member 1912, distal and proximal ends 1924,1926 ofthe splines are longitudinally collapsed toward each other, therebydeflecting the middle portions of the splines radially outwardly. Assuch, the individual ablation elements are adjusted from a firstposition (shown in FIG. 19A) to a second position (shown in FIG. 19B)wherein they are collectively arranged about a circumference to form acircumferential ablation element. Ablation elements 1930 are shown inFIG. 19B in a second position located at the outer periphery of theradially outwardly deflected splines. However, the ablation elements maybe arranged on other regions of the splines to allow for the formationof circumferential lesions of different circumferential regions oftissue. In one alternative, for example, an individual ablation element1930′ may be supported at a location along one of the splines,positioned on the distally facing portion of the spline 1925 in thesecond position, thereby forming a circumferential ablation elementadapted to ablate tissue confronted by the splines as the assembly isadvanced distally, such as for example against a posterior left atrialwall to ablate tissue surrounding a pulmonary vein.

Other alternative spline configurations to that just described for FIGS.19A–B are contemplated which are adapted to position individual ablationelements along a circumferential pattern to form a circumferentialablation element for ablating tissue along or surrounding a pulmonaryvein ostium according to the invention.

For example, circumferential ablation device assembly 2000 shown inFIGS. 20A–C provides each of a plurality of ablation elements on thedistal end portions 2026 of a plurality of longitudinally orientedspline members 2025. During use in a left atrium or pulmonary veinostium according to the invention, these spline members 2025 extenddistally from a delivery passageway 2017 (shown in FIGS. 20B & C) of acatheter body 2010 with a shape that extends radially outwardly from thelongitudinal axis of catheter body 2010. Ablation elements 2030 arethereby positioned by spline members 2025 along a circumferentialpattern about a radius R (FIG. 20B) in order to form the desiredcircumferential ablation element for ablating along or around apulmonary vein ostium according to the invention.

More specifically to the components of assembly 2000 shown in FIGS.20A–C, a delivery assembly 2000 includes an outer member 2011 that is atubular member coaxially surrounding an inner member 2012 that is also atubular member extending distally from a distal port 2018 of outermember 2011. A coaxial space is formed between outer and inner members2011,2012 and provides a delivery passageway 2017 within which splinemembers 2025 are positioned in a circumferential array (FIGS. 20B & C).Inner member 2012 includes a guidewire passageway 2015 for slideablyengaging and tracking over a guidewire. A balloon 2016, or otherexpandable member, is shown in shadow in FIG. 20A on the distal endportion of inner member 2012 and may be used in one aspect to helpanchor inner member 2012 within a pulmonary vein after inner member 2012is tracked into the vein over guidewire. As such, FIGS. 20B–C show innermember 2012 to also include a second passageway as an inflation lumen2014 in order to inflate such a balloon 2016.

The configuration shown in FIGS. 20A–B represents a second position forthe ablation elements 2030. However, in a different mode of operationduring delivery to the left atrium (not shown), the distal end portions2026 of spline members 2025 are radially confined in a longitudinalorientation within delivery passageway 2017 (FIG. 20C). Accordingly,ablation elements 2030 are thus located in a first position that isradially collapsed in relation to the second extended position throughdelivery member 2010. The ablation elements 2030 in the first positionmay remain distal to distal port 2018, such as for example if ablationelements are too large to be withdrawn through distal port 2018. Or, therespective sizes for ablation elements 2030 or delivery passageway 2017may be specifically configured to allow for the ablation elements 2030to be withdrawn into and housed within delivery passageway 2017 in thefirst position during delivery to the left atrium.

FIG. 20B further shows alternative “+” and “−” symbols associated witheach of the ablation elements 2030, one mode of this embodiment whereinablation elements 2030 provide an assembly of bipolar electrodes. Assuch, electrical current flows through tissue extending between adjacentpairs of oppositely poled electrodes, thereby ablating that tissue. Byablating tissue between all such poled pairs, a circumferential lesionmay be formed according to the invention. Further, such bipolar ablationabout the circumferential region of tissue may be accomplished in oneaspect by actuating all electrodes at once. Or, various combinations ofadjacent electrodes thereof may be gated for actuation only duringdiscrete periods of time during an overall ablation procedure. Forexample, by actuating all at once, current flowing through any givenpositively poled electrode of the array would be divided along tissue ineach opposite direction to both adjacent negatively poled electrodes.However, by providing varied duty cycles for each bipolar pair, currentmay be isolated between two adjacent poles while others of the poles arenot actuated or are left “open” and out of the circuit. Moreover, it isfurther contemplated that the ablation elements according to thisembodiment may also be monopolar electrodes or other types of ablationelements as would be apparent to one of ordinary skill based upon thisdisclosure.

Other spline member configurations than that specifically shown in FIGS.20A–C for assembly 2000 are also contemplated. For example, FIGS. 21A–Cvariously show similar assemblies to that shown in FIGS. 20A–C, but withsome specific aspects varied. More specifically, each of FIGS. 21A–Cshow a higher number of spline members 2125 and associated ablationelements 2130. This embodiment illustrating that closer spacing may berequired in some circumstances over a given circumference. Or,alternatively this illustrates that more ablation elements may be neededin order to maintain the requisite spacing between the individualelements so that a continuous circumferential lesion may be formed alongcircumferential regions of tissue with greater radii.

The distal end portions 2126 of spline members 2125 shown in FIG. 21Aillustrate different arcuate shapes that are curved about an inflectedradius relative to the corresponding shapes shown for the correspondingspline members for example in FIGS. 20A or 20C. This illustrates thatone shape may be preferred for different specific lesions to be formed.More specifically, the shapes shown in FIGS. 20A and 21C may bepreferred for ablation within a pulmonary vein ostium or vein, such thatthe curved spline members terminate with a bias that points radiallyoutwardly from the long axis of the assembly and outward toward theassociated wall to be ablated. In contrast, the shape shown in FIG. 21Ahas an inflected radius of curvature relative to the FIG. 20A/21Cembodiments, such that the distal end portions of spline members 2125are oriented with a longitudinal bias adapted to force ablation elements2130 distally relative to the longitudinal axis L of the assembly, suchas against a posterior left atrial wall in order to ablate a lesionsurrounding a pulmonary vein ostium.

Circumferential ablation device assembly 2200 shown in FIG. 22Aillustrates a further aspect of the invention wherein ablation elementsinstead extend between support structures such as the various strut orspline members herein shown and described. According to this aspect,ablation element 2230 has each of its ends 2232,2234 coupled to asupporting spline member 2225 which is adapted to adjust the ablationelement 2230 from first to second positions for delivery into the atriumand circumferential ablation, respectively, in a similar manner aspreviously described above. While this design is believed to be suitablefor either bipolar or monopolar ablation according to a specificelectrode application for the ablation element, it is believed to beparticularly well suited for circumferential ablation using theelectrode ablation elements in the monopolar fashion. Moreover, it isfurther believed that providing these ablation elements in asubstantially linear, non-preshaped structure, they would tend to stringlinearly between their ends between the spline members, yielding apattern for example such as is shown in FIG. 22B. Such pattern withsubstantially flat, linear lesion portions however may be limited inthat spline members adjusted radially outward to radius R results in acircumferential ablation that is limited to surround onlycircumferential regions, such as a pulmonary vein ostium, along ashorter radius R′. Therefore, in some instances, pre-shaped ablationelements may be desired for adjusting the pattern of the circumferentialablation element as defined along the ablative members extending betweenspline members, such as is shown in FIGS. 24A–B below.

Lines 23—23 shown in FIG. 22A are provided to illustrate that thevarious transverse cross-sectional views shown in FIGS. 23A–C showcatheter body or shaft structures that may be suitable for use accordingto the FIG. 22A embodiment, though these cross-sectioned shaftstructures may also be suitable for the other spline member embodimentsotherwise herein described for supporting and positioning ablationelements in a circumferential pattern for ablation.

More specifically, the cross-section shown in FIG. 23A shows splinemembers 2325 which are spaced around a circumference by spacers 2328that are provided in order to keep the spacing between spline members2325 controlled. Preferably, this assembly is bonded into a unitaryconstruction along the proximal aspect of the corresponding catheter,such as by soldering the splines and spacers all together, which may bedone for example within a removable capture fixture to aid in moldingthe resulting soldered assembly to the annular construction shown. Thesoldered proximal aspect and unsoldered distal aspect of thisspline/spacer assembly are positioned within a coaxial space betweenouter and inner tubing of the elongate catheter body of the overallcatheter assembly, such as between outer tubing 2311 and inner tubing2312 shown in FIGS. 23B and 23C. The outer tubing 2211 may have adiameter of about 0.120 inches. Further, the coaxial space may have aradial length of approximately 0.015 inches. FIG. 23B shows a crosssectional view taken of such an assembly as that shown in FIG. 23A,although taken along the catheter distally beyond where the spacersterminate, and further shows that the coaxial space within which theassembly may be formed may surround an inner catheter shaft 2312 havingmultiple lumens, such as for example lumens for engaging a guidewire,inflating a distal balloon, actuating the corresponding ablationelements, etc. The inner catheter shaft 2312 may have a diameter ofabout 0.042 inches.

FIG. 23C also shows a further embodiment wherein hypotube members areused to form spline members 2325′ and provide an internal lumen 2326that extend along spline members 2325′. These lumens 2326 may be usedfor example to deliver coupling members such as wires to the ablationelement(s) supported by the spline members 2325′, or fluid such as forelectrode cooling or fluidly coupled ablation such as chemical ablationor fluid-assisted electrical ablation, or may carry other elements ofthe overall assembly such as thermocouple leads. In one highlybeneficial aspect of this embodiment, such hypotubes may be constructedof a metal, such as stainless steel or nickel titanium alloy, though thescope of the invention should not be held limited as such.

A cross-section of a further assembly is shown in FIG. 23D in order toshow a further embodiment wherein a plurality of flattened members maybe used as spline members 2325″ according to the respective “spline”embodiments herein described, and may provide a highly compact assemblyof such members with relatively low radial profile as is showndimensionally in FIG. 23D. Flattened spline members 2325″ are alsobelieved to have preferential bending moment in the radial plane, withhigh structural integrity out of that plane for providing a high degreeof support during ablation.

The spline members 2325 employed in the embodiments illustrated in FIGS.23A–D may have diameters in the range of about 0.010 to about 0.020inches, more preferably ranging from about 0.013 to about 0.015 inches.Where the spline members are hypotubes, as shown in FIG. 23C, or formedfrom rolled flattened sheets, as shown in FIG. 23D, the wall thicknessof the spline members may vary from about 0.001 to about 0.005 inches.In the embodiment shown in FIG. 23A, the spacers 2328 may have separatethe spline members by approximately 0.010 to about 0.040 inches,depending on the number of spline members used.

FIG. 24A shows another “splined” circumferential ablation member 2420which has a circumferential ablation element 2428 comprised of aplurality of ablation elements 2430 provided along respective shapedelongate members 2432 extending between spline members 2425. A shapedelongate member 2432 is adapted support the ablation elements in agenerally circular circumferential pattern with an inner radius that islimited by the position of the supporting spline member, as shown inFIG. 24A, and is delivered to and from the atrium in a radiallycollapsed condition with the circumferential ablation member 2420 foldedinto a desired “convoluted” shape and the ablation elements 2420 infirst positions which are adapted for delivery in and out of a deliverysheath (not shown), as is shown in FIG. 24B. The shaped elongate member2432 may be a single unitary hoop as shown, or it may be formed fromsegments that are attached to the ends of each spline member 2425. Asshown in FIG. 24C, the shaped elongate member 2432 is actuallyintegrated portions of a continuous substantially circumferential,preshaped member that is merely engaged between portions by theindividual spline members. Further to FIG. 24C, such spline member 2425is shown to have an eyelet 2426 that forms a loop through which elongatemember 2432 is threaded. The position of spline member 2425 may belimited along elongate member 2432 such as by adhering the twostructures together, such as with adhesive or soldering, though this isbelieved to be potentially limiting in the maneuverability of thesecomponents relative to each other during operation between multiplepositions and configurations of the assembly. Alternatively, the splinemembers may be linked to the elongate member by any flexiblearticulation known in the art, such as for example interlocking eyelets,rings, sutures, etc. To provide flexibility in deployment from thecollapsed position to the radially expanded position, the eyelet 2426shown in FIG. 24C, is left somewhat freely engaged around and isrotatable about elongate member 2432, and is limited againstsubstantially moving its lateral position along elongate member 2432 byindividual ablation elements 2430 which are discrete elements providedbetween spline members along elongate member 2432.

The overall combination of spline members 2425, ablation elements 2430,elongate member 2432, and cooperating engagement between elongate member2432 and spline members 2425, through eyelets 2426, cooperate to formcircumferential ablation member 2420. Moreover, circumferential ablationmember 2420 is specifically shown in FIG. 24A with the spline members2425 adjusted radially deflected condition so as to position ablationelements 2430 along a circumferential pattern to form circumferentialablation element 2428. However, FIG. 24B illustrates ablation member2420 with ablation elements 2430 in another position which is adaptedfor delivery into and from the left atrium, such as through deliverysheath 2410. This position for ablation elements 2430 results fromadjusting spline members 2425 to a relatively radially collapsedcondition, such as after withdrawing spline members 2425 within theradially confining delivery passageway 2417 of sheath 2410. The specificembodiment shown in FIG. 24B shows elongate members and ablationelements in a relatively folded configuration relative to thecircumferential patterned position in FIG. 24A, wherein these foldedablation structures extend longitudinally away from the eyelets 2426 andterminate distally at peaks 2437 as the assembly is withdrawn oradvanced in and out of sheath 2410.

It is to be appreciated that various ablation elements herein generallydescribed above may be suitable substitutes for use with the assemblyjust described by reference to FIGS. 24A–B, wherein coiled electrodeablation elements are specifically shown in FIG. 24C. In particular withrespect to that embodiment, various electrical conductors or wires (notshown) are also to be included in the overall catheter assembly whichelectrically couple to and extend from each electrode and extendproximally from ablation member 2420 and along delivery sheath 2410and/or catheter body 2411 to a proximal electrical coupler for couplingto an electrical current source, preferably an RF current source (notshown). The ablation elements 2430 may be helical or spiral electrodesor any other electrode configurations known in the art.

For further illustration, FIG. 24D shows another type of ablationelement 2428′ incorporating a porous membrane 2460 over electrodeelements 2430 which are further provided over arcuate shaped supportmember 2432 extending between spline members (not shown). Electrodeelements 2430 are electrically coupled to tissue via electricallyconductive fluid flowing through voids or pores in porous membrane 2460and into tissue in contact therewith. Therefore, in addition to theelectrical coupling assembly as previously described above, thisembodiment further requires a fluid coupling to ablation element 2428′,which may be accomplished in one regard for example through theassociated spline members, to the extent that they may be tubular suchas hypotubes as elsewhere herein described, or via other communicatingmembers or tubing extending between the positioned circumferentialablation element and the associated delivery catheter assembly.Furthermore, such a fluid coupling aspect of this embodiment furtherincludes a proximal coupler that is adapted to couple to apressurizeable source of such an electrolytic fluid (not shown).

As would be apparent to one of ordinary skill from this disclosure,similar ablation element/actuator sub-assemblies, such as includingindividual electrodes and associated electrical conductors/couplers, orincluding fluid electrodes and associated electrical and fluid couplers,are also considered applicable to others of the various embodimentsillustrated, though they may not be specifically shown or described withreference thereto. The use of thermocouples to monitor ablationtemperature in the embodiments of the ablation devices are consideredapplicable.

FIGS. 24E–F show still a further illustrative embodiment for coupling acircumferential ablation element 2435 to associated spline members andactuating members in order to form a circumferential ablation membersuch as that shown in FIGS. 24A–B. More specifically, spline member 2425is coupled to shaped elongate member 2432 via eyelet 2426 in much thesame threaded manner as previously described for FIG. 24C. However, inthe embodiment shown in FIG. 24E, a “T”-joint coupler 2440 is furtherprovided over the spline member/elongate member coupling in order tofluidly couple a pressurized fluid source 2460 to interior spaces2434,2438 defined by porous membranes 2433,2437, respectively, whichsurrounding elongate member 2432 on either side of eyelet 2426. Morespecifically, coupler 2440 has a first leg 2441 forming a first bore2442 that receives in a fluid tight seal fluid tubing 2429 whichcoaxially surrounds spline member 2425. First leg 2441 terminates influid communication with second and third legs 2443,2445. These secondand third legs 2443,2445 form bores 2444,2446 which receive, in a fluidtight seals, terminal ends of porous members 2433,2437, alsorespectively. Accordingly, fluid tubing 2429 is provided in fluidcommunication with the interior spaces 2434,2438 of porous membranes2433, 2437, respectively, via coupler 2440.

As shown in further detail in FIG. 24F, fluid tubing 2429 and splinemember 2425 couple with catheter body 2410 through port 2418 and extendproximally through body 2410 through passageway 2417 and terminateproximally in respective couplers (not shown) for actuating the positionfor spline member 2425 and pressurizing fluid tubing 2429 with fluid. Itis to be appreciated that such fluid may be for example a chemicalablation fluid such as alcohol. Or, such fluid may be an electricallyconductive fluid in the instance that electrode elements (not shown) arefurther provided for driving current into interior spaces 2434,2438 ofporous membranes 2433,2437, respectively, as would be apparent to one ofordinary skill from this disclosure.

Other moveable engagement means are contemplated as suitable substitutesfor the specific “eyelet” embodiment shown in FIG. 24C. One suchalternative means is shown in various modes in FIGS. 25A–B, whereinspline members 2525 terminate proximally in balls 2536 which couple toreceivers 2526 in a “ball-in-socket” type of coupling that allows for apredetermined range of relative movement between these components toallow for the transition between radially collapsed and expanded orextended conditions for spline members 2525 and the corresponding firstand second positions for ablation element 2530 (compare FIGS. 25A and B,respectively).

Additional variations for the spline members are further contemplated assuitable substitutes for those previously described above, such as byspecific reference to spline members 2425 shown in FIG. 24A.

One such illustrative embodiment is shown in FIGS. 26A–B, wherein splinemembers 2625 are provided with predetermined arcuate and convolutedshapes. More specifically, FIG. 26C shows in detail spline member 2625which is constructed from a shaped member 2621 having two legs 2622,2624extending in a side-by-side relationship between proximal end portion2627 and distal end portion 2628 of spline member 2625. Shaped member2621 forms an acute bend or loop between legs 2622,2624 at distal endportion 2628. Circumferential ablation element 2635 is threaded througha plurality of such loops formed by multiple such spline members 2625about a circumferential pattern, as shown in a first configuration inFIG. 26A. The ablation element may comprise a plurality of individualablation electrodes 2630 as illustrated, or alternatively, the ablationelement may comprise a continuous ablation coil or helix, as illustratedwith reference to FIG. 24A. This assembly is further collapsible througha delivery catheter 2610, as shown in FIG. 26B, in which configurationthe circumferential ablation element 2635 may form convoluted folds2635′ extending proximally from distal ends 2628 to proximal ends 2627of spline members 2625, as shown in greater detail in FIG. 26C. Or, suchfolds may extend away from spline members 2625, such as in a similarmanner to that shown in FIG. 24B. The desired folded configuration maybe controlled, such as for example by forming a pre-shaped bias ormemory to the circumferential ablation element that is elasticallydeflected into the circumferential pattern by the corresponding splinemembers, or in another example by providing tethers to pull on portionsof the ablation element such as in order to yield the folded geometry ofFIG. 26C. Furthermore, in some instances the mechanical action ofretracting spline members within the corresponding delivery sheath orcatheter may cause the folds to “groom” into the configuration shown inFIG. 24B, since the splines are effectively pulling the ablation elementinto the sheath.

The specific geometry shown and just described for spline members 2625by reference to FIGS. 26A–C is also believed to be beneficial foradapting the desired circumferential ablation element to ablate regionsof tissue against the posterior left atrial wall and surrounding apulmonary vein. More specifically, the side-by-side leg configurationsbordered in the middle by a bended loop is believed to provide a robustsupport structure along the plane along which the circumferentialablation element is patterned. Notwithstanding this feature, however,such shaped spline structures may be further provided with angledorientations out of the plane of the resulting circumferential ablationelement's shape without departing from the scope of the invention.Additionally, the opposing concavity and convexity of the reciprocallyshaped legs provides wider base of their separation along the proximaland distal end portions 2627,2628 than along a mid region 2626, suchthat there is robust support along the proximal and distal end portions,but an overall flexibility provided by the mid region 2626.

A further circumferential ablation member 2720 according to theinvention is shown variously in FIGS. 27A–28D and provides a similarassembly of shaped spline members 2725 as that shown in FIGS. 26A–Cwithin a housing 2740 which is adjustable to provide a distal wall 2760(shown in FIGS. 27C & D) having a circumferential surface 2745 thatforms at least in part a circumferential ablation element for ablatingtissue surrounding a pulmonary vein ostium according to the invention.More specifically, spline members 2725 are provided between distal wall2760 and a proximal wall 2750 which are shown in FIGS. 27C & D to berelatively taut opposing faces when spline members 2725 are in aradially extended condition relative to longitudinal axis L of deliverymember 2710. By reference to this extended and taut condition shown inFIG. 27A, proximal and distal walls 2750,2760 are sealed together alongboth an inner circumferential region 2741 and an outer circumferentialregion 2743 relative to the extended condition for spline members 3125and corresponding taut condition for housing 2740 shown in FIG. 27A.

The proximal 2750 and distal 2760 walls are not sealed to one another inthe intermediate circumferential region 2745 between the sealed innerand outer portions 2741, 2743, respectively, along this radius, yieldinga void space between the walls in that circumferential region, but forthe presence of the spline members 2725 which extend between all threeof the respectively sealed and unsealed regions as shown in FIG. 27A.Distal wall 2760 is porous along the unsealed circumferential region2745. In a variation of this embodiment, shown in FIGS. 28A and 28D, thevoid space is created in the unsealed circumferential region 2845 by aconcave region of the distal wall 2860. As shown in greater detail inFIG. 27C, a fluid tubing 2729 is positioned between proximal and distalwalls 2750,2760 and terminates along unsealed circumferential region2745 such that this void space communicates externally of housing 2740only through fluid tubing 2729 and the pores along the porous portion ofdistal wall 2760 along that circumference. The same fluid couplingrelationship is also illustrated in FIGS. 28A & B. Fluid tubing 2729 andspline members 2725 couple proximally to various lumens or passageways(not shown) provided by delivery member 2710, as shown in part in FIG.27C, and are further coupled to corresponding actuators as elsewhereherein described.

Further to the sealed regions 2741,2743 for housing 2740, an adhesive orother sufficient filler material may be used in order to ensure a fluidtight seal around the fluid tubing 2729 and spline members 2725 andbetween the housing's respectively sealed walls, as shown alongintermediate layer 2747 between proximal and distal walls 2750,2760 inFIG. 27D.

When circumferential ablation member 2720 is withdrawn into a deliverysheath (not shown), spline members 2725 are adjusted to a radiallycollapsed condition which adjusts the housing 2740 to a folded positionthat is adapted for delivery to and from the atrium for ablation (notshown). Once in the left atrium, spline members 2725 are advanceddistally from the delivery sheath in the radially extended condition asshown in FIGS. 27A–B. Accordingly, circumferential region 2745 ispositioned to form a circumferential ablation element when an ablativefluid couples to tissue through the porous portion of distal wall 2760along that region. As previously described for other embodiments, thisfluid coupling may include for example a chemically ablative fluid, ormay incorporate an electrically conductive fluid energized with currentfrom electrodes, such as shown schematically at electrodes 2730 whichare positioned along spline members along the porous and ablativecircumferential region 2745. It is further contemplated that theelongated member forming the spline members 2725 themselves may beelectrically conductive, such as a conductive metal construction, andprovide such electrode function over an above the support andpositioning functions otherwise herein described.

A further circumferential ablation member 2820 forming an ablativecircumferential region along a distal wall of a radially adjustablehousing is shown in FIGS. 28A–C. This embodiment however allows for theradial adjustment of a housing 2840 by manipulation of cooperatingportions of catheter body 2810 and without the need for withdrawal oradvancement of a separate, confining delivery sheath as with the FIG. 26and FIG. 27 embodiments.

With reference to FIGS. 28A & B, a molded insert or tip housing isshown. The housing, which may be constructed out of metal or moldedplastic for example, may be used for coupling the circumferentialablation member components to the corresponding catheter, as shown attip housing 2812 in FIG. 28B. With reference to FIGS. 28C and 28D, thespline members 2825 are shown in cross section extending in an innercircumferential region between the sealed proximal 2850 and distal 2860walls, and in an outer circumferential region within the void spacebetween these walls.

With reference to FIGS. 29A–30D, other variations of the circumferentialablation device assembly are shown, which include a circumferentialablation member located along a distal end portion of catheter body andincludes a housing that forms a porous distal wall that covers thedistal end portions of a plurality of spline members. In one embodiment,the distal tip of the elongate or catheter body may include an anchor(e.g., inflatable balloon), and/or a distal port of for a guidewire.Each of spline members includes: a proximal end portion that is securedto outer member of catheter body; a distal end portion that is securedto an inner member extending from within outer member and distally fromcircumferential ablation member; and a hinge point between correspondingproximal and distal end portions.

As shown in FIG. 29A, by moving outer member 2911 distally with respectto inner member 2912, the respective proximal and distal end portions2922,2926 of spline members 2925 are adapted to longitudinally collapsewith respect to longitudinal axis L of body such that hinge point 2924deflects radially outwardly from longitudinal axis L. This radialdeflection of the spline members 2925 causes a distal wall 2960 coveringdistal end portions 2926 to be angled with a distal orientation. Distalwall 2960 has a circumferential ablative surface 2961 that is adapted toablate a circumferential region of tissue in contact therewith.

FIGS. 29A & B show that housing 2940 includes proximal and distal walls2950,2960 which are either separate members secured together or areseparately treated portions of one otherwise contiguous, integrallyformed member. Proximal wall 2950 covers proximal end portions 2922 ofspline members 2925 and is secured in a fluid tight seal over outermember 2911 proximally of circumferential ablation member 2920. Distalwall 2960 covers distal end portions 2926 of spline members 2925 and issecured in a fluid tight seal over inner member 2912 distally ofcircumferential ablation member 2920. As in previous embodiments, theinner member 2912 is adapted to track over guidewire 2902. The distalend portions 2926 of spline members 2925 are shown in FIG. 29B asincorporating ablation electrodes 2930. A pressurizeable fluid source2903 is fluidly coupled to an interior space formed by housing 2940 viathe co-axial space formed between outer and inner members 2911,2912, asshown schematically in FIG. 29A.

Spline members 2925 may be made by cutting longitudinal grooves intoouter member 2911, but should not be limited as such. For example,spline members 2925 may alternatively be separate components secured toouter and inner members 2911,2912, such as for example separate shapedmembers such as spline members 2625 shown and described by reference toFIGS. 26A and C. Further to that variation, hinge point 2924 may beformed along the more flexible, converging, narrowed separation betweenseparate struts, such as at 2626 shown in FIG. 26C.

In another specific embodiment, the electrode elements 2930 isincorporated along spline members 2925. In this embodiment, distal wall2960 is porous along circumferential ablative surface 2961, and housing2940 further includes a backing or proximal wall (not shown) that coversproximal end portions 2922 of spline members 2925.

With reference to FIG. 30A, inner member 3012 includes a fluidpassageway terminating in ports 3017 located within housing 3040, and agasket seal 3013 is provided between outer and inner members 3011,3012proximally of fluid ports 3017 and ablation member 3020. Accordingly,with the ablation member 3020 in the radially expanded condition andablative surface 3061 positioned for ablation as shown in FIGS. 30A–C,electrolyte fluid filling housing 3040 can only escape through theporous region along ablative surface 3061, thereby electrically couplingablation elements 3030 with tissue contacting that surface 3061 such asa circumferential region of tissue surrounding a pulmonary vein ostium.

With reference to FIGS. 30B & C, proximal and distal perspective viewsare illustrated. The proximal wall 3050 of housing 3040 can be seen inFIG. 30B to substantially cover the proximal surfaces of the splinemembers (shown in phantom).

Further to the various embodiments just described incorporating housingsthat are controllably positioned by use of deflectable spline members,the porous wall aspects of such embodiments may be constructed accordingto several known structures and methods. Porous fluoropolymers such asporous polytetrafluoroethylene (PTFE), and in particular the expandedvariety (e-PTFE), may be suitable. In such case, however, thecorresponding porous wall would be relatively non-elastomeric, andtherefore must be adjusted between folded and taut conditions betweenthe delivery and ablation positions described by reference to theparticular embodiments. However, such porous material may also beconstructed from an elastomer, such as for example a porous siliconematerial, which beneficially may have an elastomeric memory to a tubularstate in the corresponding delivery position and which stretches to theablation positions as herein described. Such porous elastomer embodimentis believed to be highly beneficial for use in the embodiments describedby reference to FIGS. 33A–34F, wherein the corresponding housingincluding a porous region may be substantially tubular along therespective catheter assembly. Further to this aspect, it is furthercontemplated that such housings such as housing 3040 shown in FIGS.30A–D may be constructed of a contiguous elastomeric tube which has beenmade porous along only the ablative circumferential surface of thedistal wall 3060 in the resulting assembly.

FIGS. 31A–34B show various specific embodiments of a circumferentialablation device assembly that utilizes an ultrasonic energy source toablate tissue. The present circumferential ablation device hasparticular utility in connection with forming a circumferential lesionwithin or about a pulmonary vein ostium or within the vein itself inorder to form a circumferential conductive block. This application ofthe present ablation device, however, is merely exemplary, and it isunderstood that those skilled in the art can readily adapt the presentablation device for applications in other body spaces.

As common to each of the following embodiments, a source of acousticenergy is provided a delivery device that also includes an anchoringmechanism. In one mode, the anchoring device comprises an expandablemember that also positions the acoustic energy source within the body;however, other anchoring and positioning devices may also be used, suchas, for example, a basket mechanism. In a more specific form, theacoustic energy source is located within the expandable member and theexpandable member is adapted to engage a circumferential path of tissueeither about or along a pulmonary vein in the region of its ostium alonga left atrial wall. The acoustic energy source in turn is acousticallycoupled to the wall of the expandable member and thus to thecircumferential region of tissue engaged by the expandable member wallby emitting a circumferential and longitudinally collimated ultrasoundsignal when actuated by an acoustic energy driver. The use of acousticenergy, and particularly ultrasonic energy, offers the advantage ofsimultaneously applying a dose of energy sufficient to ablate arelatively large surface area within or near the heart to a desiredheating depth without exposing the heart to a large amount of current.For example, a collimated ultrasonic transducer can form a lesion, whichhas about a 1.5 mm width, about a 2.5 mm diameter lumen, such as apulmonary vein and of a sufficient depth to form an effective conductiveblock. It is believed that an effective conductive block can be formedby producing a lesion within the tissue that is transmural orsubstantially transmural. Depending upon the patient as well as thelocation within the pulmonary vein ostium, the lesion may have a depthof about 1 to 10 mm. It has been observed that the collimated ultrasonictransducer can be powered to provide a lesion having these parameters soas to form an effective conductive block between the pulmonary vein andthe posterior wall of the left atrium.

With specific reference now to the embodiment illustrated in FIGS. 31Athrough 31D, a circumferential ablation device assembly 800 includes anelongate catheter body 802 with proximal and distal end portions810,812, an expandable balloon 820 located along the distal end portion812 of elongate catheter body 802, and a circumferential ultrasoundtransducer 830 which forms a circumferential ablation member that isacoustically coupled to the expandable balloon 820. In more detail,FIGS. 31A–C variously show elongate catheter body 802 to includeguidewire lumen 804, inflation lumen 806, and electrical lead lumen 808.The ablation device, however, can be of a self-steering type rather thanan over-the-wire type device.

Each lumen extends between a proximal port (not shown) and a respectivedistal port, which distal ports are shown as distal guidewire port 805for guidewire lumen 804, distal inflation port 807 for inflation lumen806, and distal lead port 809 for electrical lead lumen 808. Althoughthe guidewire, inflation and electrical lead lumens are generallyarranged in a side-by-side relationship, the elongate catheter body 802can be constructed with one or more of these lumens arranged in acoaxial relationship, or in any of a wide variety of configurations thatwill be readily apparent to one of ordinary skill in the art.

In addition, the elongate catheter body 802 is also shown in FIGS. 31Aand 31C to include an inner member 803 that extends distally beyonddistal inflation and lead ports 807,809, through an interior chamberformed by the expandable balloon 820, and distally beyond expandableballoon 820 where the elongate catheter body terminates in a distal tip.The inner member 803 forms the distal region for the guidewire lumen 804beyond the inflation and lead ports, and also provides a support memberfor the cylindrical ultrasound transducer 830 and for the distal neck ofthe expansion balloon, as described in more detail below.

One more detailed construction for the components of the elongatecatheter body 802 that is believed to be suitable for use in transeptalleft atrial ablation procedures is as follows. The elongate catheterbody 802 itself may have an outer diameter provided within the range offrom about 5 French to about 10 French, and more preferable from about 7French to about 9 French. The guidewire lumen preferably is adapted toslideably receive guidewires ranging from about 0.010 inch to about0.038 inch in diameter, and preferably is adapted for use withguidewires ranging from about 0.018 inch to about 0.035 inch indiameter. Where a 0.035 inch guidewire is to be used, the guidewirelumen preferably has an inner diameter of 0.040 inch to about 0.042inch. In addition, the inflation lumen preferably has an inner diameterof about 0.020 inch in order to allow for rapid deflation times,although may vary based upon the viscosity of inflation medium used,length of the lumen, and other dynamic factors relating to fluid flowand pressure.

In addition to providing the requisite lumens and support members forthe ultrasound transducer assembly, the elongate catheter body 802 ofthe present embodiment must also be adapted to be introduced into theleft atrium such that the distal end portion with balloon and transducermay be placed within the pulmonary vein ostium in a percutaneoustranslumenal procedure, and even more preferably in a transeptalprocedure as otherwise herein provided. Therefore, the distal endportion 812 is preferably flexible and adapted to track over and along aguidewire seated within the targeted pulmonary vein. In one further moredetailed construction that is believed to be suitable, the proximal endportion is adapted to be at least 30% stiffer than the distal endportion. According to this relationship, the proximal end portion may besuitably adapted to provide push transmission to the distal end portionwhile the distal end portion is suitably adapted to track throughbending anatomy during in vivo delivery of the distal end portion of thedevice into the desired ablation region.

Notwithstanding the specific device constructions just described, otherdelivery mechanisms for delivering the ultrasound ablation member to thedesired ablation region are also contemplated. For example, while theFIG. 31A variation is shown as an “over-the-wire” catheter construction,other guidewire tracking designs may be suitable substitutes, such as,for example, catheter devices which are known as “rapid exchange” or“monorail” variations wherein the guidewire is only housed coaxiallywithin a lumen of the catheter in the distal regions of the catheter. Inanother example, a deflectable tip design may also be a suitablesubstitute and which is adapted to independently select a desiredpulmonary vein and direct the transducer assembly into the desiredlocation for ablation. Further to this latter variation, the guidewirelumen and guidewire of the FIG. 31A variation may be replaced with a“pullwire” lumen and associated fixed pullwire which is adapted todeflect the catheter tip by applying tension along varied stiffnesstransitions along the catheter's length. Still further to this pullwirevariation, acceptable pullwires may have a diameter within the rangefrom about 0.008 inch to about 0.020 inch, and may further include ataper, such as, for example, a tapered outer diameter from about 0.020inch to about 0.008 inch.

More specifically regarding expandable balloon 820 as shown in varieddetail between FIGS. 31A and 31C, a central region 822 is generallycoaxially disposed over the inner member 803 and is bordered at its endneck regions by proximal and distal adaptions 824,826. The proximaladaption 824 is sealed over elongate catheter body 802 proximally of thedistal inflation and the electrical lead ports 807,809, and the distaladaption 826 is sealed over inner member 803. According to thisarrangement, a fluid tight interior chamber is formed within expandableballoon 820. This interior chamber is fluidly coupled to apressurizeable fluid source (not shown) via inflation lumen 806. Inaddition to the inflation lumen 806, electrical lead lumen 808 alsocommunicates with the interior chamber of expandable balloon 820 so thatthe ultrasound transducer 830, which is positioned within that chamberand over the inner member 803, may be electrically coupled to anultrasound drive source or actuator, as will be provided in more detailbelow.

The expandable balloon 820 may be constructed from a variety of knownmaterials, although the balloon 820 preferably is adapted to conform tothe contour of a pulmonary vein ostium. For this purpose, the balloonmaterial can be of the highly compliant variety, such that the materialelongates upon application of pressure and takes on the shape of thebody lumen or space when fully inflated. Suitable balloon materialsinclude elastomers, such as, for example, but without limitation,Silicone, latex, or low durometer polyurethane (for example, a durometerof about 80 A).

In addition or in the alternative to constructing the balloon of highlycompliant material, the balloon 820 can be formed to have a predefinedfully inflated shape (i.e., be preshaped) to generally match theanatomic shape of the body lumen in which the balloon is inflated. Forinstance, as described below in greater detail, the balloon can have adistally tapering shape to generally match the shape of a pulmonary veinostium, and/or can include a bulbous proximal end to generally match atransition region of the atrium posterior wall adjacent to the pulmonaryvein ostium. In this manner, the desired seating within the irregulargeometry of a pulmonary vein or vein ostium can be achieved with bothcompliant and non-compliant balloon variations.

Notwithstanding the alternatives that may be acceptable as justdescribed, the balloon 820 is preferably constructed to exhibit at least300% expansion at 3 atmospheres of pressure, and more preferably toexhibit at least 400% expansion at that pressure. The term “expansion”is herein intended to mean the balloon outer diameter afterpressurization divided by the balloon inner diameter beforepressurization, wherein the balloon inner diameter before pressurizationis taken after the balloon is substantially filled with fluid in a tautconfiguration. In other words, “expansion” is herein intended to relateto change in diameter that is attributable to the material compliance ina stress strain relationship. In one more detailed construction which isbelieved to be suitable for use in most conduction block procedures inthe region of the pulmonary veins, the balloon is adapted to expandunder a normal range of pressure such that its outer diameter may beadjusted from a radially collapsed position of about 5 mm to a radiallyexpanded position of about 2.5 cm (or approximately 500% expansionratio).

The ablation member illustrated in FIGS. 31A–D, takes the form ofannular ultrasonic transducer 830. In the illustrated embodiment, theannular ultrasonic transducer 830 has a unitary cylindrical shape with ahollow interior (i.e., is tubular shaped); however, the transducerapplicator 830 can have a generally annular shape and be formed of aplurality of segments. For instance, the transducer applicator 830 canbe formed by a plurality of tube sectors that together form an annularshape. The tube sectors can also be of sufficient arc lengths so as whenjoined together, the sector assembly forms a “clover-leaf” shape. Thisshape is believed to provide overlap in heated regions between adjacentelements. The generally annular shape can also be formed by a pluralityof planar transducer segments that are arranged in a polygon shape(e.g., hexagon). In addition, although in the illustrated embodiment theultrasonic transducer comprises a single transducer element, thetransducer applicator can be formed of a multi-element array, asdescribed in greater detail below.

As is shown in detail in FIG. 31D, cylindrical ultrasound transducer 830includes a tubular wall 831 with three concentric tubular layers. Thecentral layer 832 is a tubular shaped member of a piezoceramic orpiezoelectric crystalline material. The transducer preferably is made oftype PZT-4, PZT-5 or PZT-8, quartz or Lithium-Niobate type piezoceramicmaterial to ensure high power output capabilities. These types oftransducer materials are commercially available from Stavely Sensors,Inc. of East Hartford, Conn., or from Valpey-Fischer Corp. of Hopkinton,Mass.

The outer and inner tubular members 833,834 enclose central layer 832within their coaxial space and are constructed of an electricallyconductive material. In the illustrated embodiment, these transducerelectrodes 833,834 comprise a metallic coating, and more preferably acoating of nickel, copper, silver, gold, platinum, or alloys of thesemetals.

One more detailed construction for a cylindrical ultrasound transducerfor use in the present application is as follows. The length of thetransducer 830 or transducer assembly (e.g., multi-element array oftransducer elements) desirably is selected for a given clinicalapplication. In connection with forming circumferential conductionblocks in cardiac or pulmonary vein wall tissue, the transducer lengthcan fall within the range of approximately 2 mm up to greater than 10mm, and preferably equals about 5 to 10 mm. A transducer accordinglysized is believed to form a lesion of a width sufficient to ensure theintegrity of the formed conductive block without undue tissue ablation.For other applications, however, the length can be significantly longer.

Likewise, the transducer outer diameter desirably is selected to accountfor delivery through a particular access path (e.g., percutaneously andtransseptally), for proper placement and location within a particularbody space, and for achieving a desired ablation effect. In the givenapplication within or proximate of the pulmonary vein ostium, thetransducer 830 preferably has an outer diameter within the range ofabout 1.8 mm to greater than 2.5 mm. It has been observed that atransducer with an outer diameter of about 2 mm generates acoustic powerlevels approaching 20 Watts per centimeter radiator or greater withinmyocardial or vascular tissue, which is believed to be sufficient forablation of tissue engaged by the outer balloon for up to about 2 cmouter diameter of the balloon. For applications in other body spaces,the transducer applicator 830 may have an outer diameter within therange of about 1 mm to greater than 3–4 mm (e.g., as large as 1 to 2 cmfor applications in some body spaces).

The central layer 832 of the transducer 830 has a thickness selected toproduce a desired operating frequency. The operating frequency will varyof course depending upon clinical needs, such as the tolerable outerdiameter of the ablation and the depth of heating, as well as upon thesize of the transducer as limited by the delivery path and the size ofthe target site. As described in greater detail below, the transducer830 in the illustrated application preferably operates within the rangeof about 5 MHz to about 20 MHz, and more preferably within the range ofabout 7 MHz to about 10 MHz. Thus, for example, the transducer can havea thickness of approximately 0.3 mm for an operating frequency of about7 MHz (i.e., a thickness generally equal to ½ the wavelength associatedwith the desired operating frequency).

The transducer 830 is vibrated across the wall thickness and to radiatecollimated acoustic energy in the radial direction. For this purpose, asbest seen in FIGS. 31A and 31D, the distal ends of electrical leads836,837 are electrically coupled to outer and inner tubular members orelectrodes 833,834, respectively, of the transducer 830, such as, forexample, by soldering the leads to the metallic coatings or byresistance welding. In the illustrated embodiment, the electrical leadsare 4–8 mil (0.004 to 0.008 inch diameter) silver wire or the like.

The proximal ends of these leads are adapted to couple to an ultrasonicdriver or actuator 840, which is schematically illustrated in FIG. 31D.FIGS. 31A–D further show leads 836,837 as separate wires withinelectrical lead lumen 808, in which configuration the leads must be wellinsulated when in close contact. Other configurations for leads 836,837are therefore contemplated. For example, a coaxial cable may provide onecable for both leads that is well insulated as to inductanceinterference. Or, the leads may be communicated toward the distal endportion 812 of the elongate catheter body through different lumens thatare separated by the catheter body.

The transducer also can be sectored by scoring or notching the outertransducer electrode 833 and part of the central layer 832 along linesparallel to the longitudinal axis L of the transducer 830, asillustrated in FIG. 31E. A separate electrical lead connects to eachsector in order to couple the sector to a dedicated power control thatindividually excites the corresponding transducer sector. By controllingthe driving power and operating frequency to each individual sector, theultrasonic driver 840 can enhance the uniformity of the ultrasonic beamaround the transducer 830, as well as can vary the degree of heating(i.e., lesion control) in the angular dimension.

The ultrasound transducer just described is combined with the overalldevice assembly according to the present embodiment as follows. Inassembly, the transducer 830 desirably is “air-backed” to produce moreenergy and to enhance energy distribution uniformity, as known in theart. In other words, the inner member 803 does not contact anappreciable amount of the inner surface of transducer inner tubularmember 834. This is because the piezoelectric crystal which formscentral layer 832 of ultrasound transducer 830 is adapted to radiallycontract and expand (or radially “vibrate”) when an alternating currentis applied from a current source and across the outer and inner tubularelectrodes 833,834 of the crystal via the electrical leads 836,837. Thiscontrolled vibration emits the ultrasonic energy that is adapted toablate tissue and form a circumferential conduction block according tothe present embodiment. Therefore, it is believed that appreciablelevels of contact along the surface of the crystal may provide adampening effect that would diminish the vibration of the crystal andthus limit the efficiency of ultrasound transmission.

For this purpose, the transducer 830 seats coaxial about the innermember 803 and is supported about the inner member 803 in a mannerproviding a gap between the inner member 803 and the transducer innertubular member 834. That is, the inner tubular member 834 forms aninterior bore 835 that loosely receives the inner member 803. Any of avariety of structures can be used to support the transducer 830 aboutthe inner member 803. For instance, spacers or splines can be used tocoaxially position the transducer 830 about the inner member 803 whileleaving a generally annular space between these components. In thealternative, other conventional and known approaches to support thetransducer can also be used. For instance, O-rings that circumscribe theinner member 803 and lie between the inner member 803 and the transducer830 can support the transducer 830 in a manner similar to thatillustrated in U.S. Pat. No. 5,606,974 to Castellano issued Mar. 4,1997, and entitled “Catheter Having Ultrasonic Device.” More detailedexamples of the alternative transducer support structures just describedare disclosed in U.S. Pat. No. 5,620,479 to Diederich, issued Apr. 15,1997, and entitled “Method and Apparatus for Thermal Therapy of Tumors.”

The disclosures of these references are herein incorporated in theirentirety by reference thereto.

In the illustrated embodiment, at least one stand-off region 838 isprovided along inner member 803 in order to ensure that the transducer830 has a radial separation from the inner member 803 to form a gapfilled with air and/or other fluid. In one preferred mode shown in FIG.31C, stand-off region 838 is a tubular member with a plurality ofcircumferentially spaced outer splines 839 that hold the majority of thetransducer inner surface away from the surface of the stand-off betweenthe splines, thereby minimizing dampening affects from the coupling ofthe transducer to the catheter. The tubular member that forms astand-off such as stand-off region 838 in the FIG. 31C embodiment mayalso provide its inner bore as the guidewire lumen in the region of theultrasound transducer, in the alternative to providing a separatestand-off coaxially over another tubular member which forms the innermember, such as according to the FIG. 31C embodiment.

In a further mode, the elongate catheter body 802 can also includeadditional lumens which lie either side by side to or coaxial with theguidewire lumen 804 and which terminate at ports located within thespace between the inner member 803 and the transducer 830. A coolingmedium can circulate through space defined by the stand-off 838 betweenthe inner member 803 and the transducer 830 via these additional lumens.By way of example, carbon dioxide gas, circulated at a rate of 5 litersper minute, can be used as a suitable cooling medium to maintain thetransducer at a lower operating temperature. It is believed that suchthermal cooling would allow more acoustic power to transmit to thetargeted tissue without degradation of the transducer material.

The transducer 830 desirably is electrically and mechanically isolatedfrom the interior of the balloon 820. Again, any of a variety ofcoatings, sheaths, sealants, tubing and the like may be suitable forthis purpose, such as those described in U.S. Pat. No. 5,620,479 toDiederich and U.S. Pat. No. 5,606,974 to Castellano. In the illustratedembodiment, as best illustrated in FIG. 31C, a conventional, flexible,acoustically compatible, and medical grade epoxy 842 is applied over thetransducer 830. The epoxy 842 may be, for example, Epotek 301, Epotek310, which is available commercially from Epoxy Technology, or TraconFDA-8. In addition, a conventional sealant, such as, for example,General Electric Silicon II gasket glue and sealant, desirably isapplied at the proximal and distal ends of the transducer 830 around theexposed portions of the inner member 803, wires 836,837 and stand-offregion 838 to seal the space between the transducer 830 and the innermember 803 at these locations.

An ultra thin-walled polyester heat shrink tubing 844 or the like thenseals the epoxy coated transducer. Alternatively, the epoxy coveredtransducer 830, inner member 803 along stand-off region 838 can beinstead inserted into a tight thin wall rubber or plastic tubing madefrom a material such as Teflon®, polyethylene, polyurethane, silastic orthe like. The tubing desirably has a thickness of 0.0005 to 0.003inches.

When assembling the ablation device assembly, additional epoxy isinjected into the tubing after the tubing is placed over the epoxycoated transducer 830. As the tube shrinks, excess epoxy flows out and athin layer of epoxy remains between the transducer and the heat shrinktubing 844. These layers 842,844 protect the transducer surface, helpacoustically match the transducer 830 to the load, makes the ablationdevice more robust, and ensures air-tight integrity of the air backing.

Although not illustrated in FIG. 31A in order to simplify the drawing,the tubing 844 extends beyond the ends of transducer 830 and surrounds aportion of the inner member 803 on either side of the transducer 830. Afiller (not shown) can also be used to support the ends of the tubing844. Suitable fillers include flexible materials such as, for example,but without limitation, epoxy, Teflon® tape and the like.

The ultrasonic actuator 840 generates alternating current to power thetransducer 830. The ultrasonic actuator 840 drives the transducer 830 atfrequencies within the range of about 5 MHz to about 20 MHz, andpreferably for the illustrated application within the range of about 7MHz to about 10 MHz. In addition, the ultrasonic driver can modulate thedriving frequencies and/or vary power in order to smooth or unify theproduced collimated ultrasonic beam. For instance, the functiongenerator of the ultrasonic actuator 840 can drive the transducer atfrequencies within the range of 6.8 MHz and 7.2 MHz by continuously ordiscretely sweeping between these frequencies.

The ultrasound transducer 830 of the present embodiment sonicallycouples with the outer skin of the balloon 820 in a manner that forms acircumferential conduction block at a location where a pulmonary veinextends from an atrium as follows. Initially, the ultrasound transduceris believed to emit its energy in a circumferential pattern that ishighly collimated along the transducer's length relative to itslongitudinal axis L (see FIG. 16D). The circumferential band thereforemaintains its width and circumferential pattern over an appreciablerange of diameters away from the source at the transducer. Also, theballoon is preferably inflated with fluid that is relativelyultrasonically transparent, such as, for example, degassed water.Therefore, by actuating the transducer 830 while the balloon 820 isinflated, the circumferential band of energy is allowed to translatethrough the inflation fluid and ultimately sonically couple with acircumferential band of balloon skin that circumscribes the balloon 820.Moreover, the circumferential band of balloon skin material may also befurther engaged along a circumferential path of tissue whichcircumscribes the balloon, such as, for example, if the balloon isinflated within and engages a pulmonary vein wall, ostium, or region ofatrial wall. Accordingly, where the balloon is constructed of arelatively ultrasonically transparent material, the circumferential bandof ultrasound energy is allowed to pass through the balloon skin andinto the engaged circumferential path of tissue such that thecircumferential path of tissue is ablated.

Further to the transducer-balloon relationship just described, theenergy is coupled to the tissue largely via the inflation fluid andballoon skin. It is believed that, for in vivo uses of the presentinvention, the efficiency of energy coupling to the tissue, andtherefore ablation efficiency, may significantly diminish incircumstances where there is poor contact and conforming interfacebetween the balloon skin and the tissue. Accordingly, it is contemplatedthat several different balloon types may be provided for ablatingdifferent tissue structures so that a particular shape may be chosen fora particular region of tissue to be ablated.

In one particular balloon-transducer combination shown in FIG. 31A andalso in FIG. 33A, the ultrasound transducer preferably has a length suchthat the ultrasonically coupled band of the balloon skin, having asimilar length d according to the collimated ultrasound signal, isshorter than the working length D of the balloon. According to thisaspect of the relationship, the transducer is adapted as acircumferential ablation member that is coupled to the balloon to forman ablation element along a circumferential band of the balloon,therefore forming a circumferential ablation element band thatcircumscribes the balloon. Preferably, the transducer has a length thatis less than two-thirds the working length of the balloon, and morepreferably is less than one-half the working length of the balloon. Bysizing the ultrasonic transducer length d smaller than the workinglength D of the balloon 820—and hence shorter than a longitudinal lengthof the engagement area between the balloon 820 and the wall of the bodyspace (e.g., pulmonary vein ostium)—and by generally centering thetransducer 830 within the balloon's working length D, the transducer 830operates in a field isolated from the blood pool. A generally equatorialposition of the transducer 830 relative to the ends of the balloon'sworking length also assists in the isolation of the transducer 830 fromthe blood pool. It is believed that the transducer placement accordingto this arrangement may be preventative of thrombus formation that mightotherwise occur at a lesion sight, particularly in the left atrium.

The ultrasound transducer described in various levels of detail abovehas been observed to provide a suitable degree of radiopacity forlocating the energy source at a desired location for ablating theconductive block. However, it is further contemplated that the elongatecatheter body 802 may include an additional radiopaque marker or markers(not shown) to identify the location of the ultrasonic transducer 830 inorder to facilitate placement of the transducer at a selected ablationregion of a pulmonary vein via X-ray visualization. The radiopaquemarker is opaque under X-ray, and can be constructed, for example, of aradiopaque metal such as gold, platinum, or tungsten, or can comprise aradiopaque polymer such as a metal loaded polymer. The radiopaque markeris positioned coaxially over an inner tubular member 803, in a mannersimilar to that described in connection with the embodiment of FIG. 13.

The present circumferential ablation device is introduced into apulmonary vein of the left atrium in a manner similar to that describedabove. Once properly positioned within the pulmonary vein or veinostium, the pressurized fluid source inflates the balloon 820 to engagethe lumenal surface of the pulmonary vein ostium. Once properlypositioned, the ultrasonic driver 840 is energized to drive thetransducer 830. It is believed that by driving the ultrasonic transducer830 at 20 acoustical watts at an operating frequency of 7 MHz, that asufficiently sized lesion can be formed circumferentially about thepulmonary vein ostium in a relatively short period of time (e.g., 1 to 2minutes or less). It is also contemplated that the control level ofenergy can be delivered, then tested for lesion formation with a teststimulus in the pulmonary vein, either from an electrode provided at thetip area of the ultrasonic catheter or on a separate device such as aguidewire through the ultrasonic catheter. Therefore, the procedure mayinvolve ablation at a first energy level in time, then check for theeffective conductive block provided by the resulting lesion, and thensubsequent ablations and testing until a complete conductive block isformed. In the alternative, the circumferential ablation device may alsoinclude feedback control, for example, if thermocouples are provided atthe circumferential element formed along the balloon outer surface.Monitoring temperature at this location provides indicia for theprogression of the lesion. This feedback feature may be used in additionto or in the alternative to the multi-step procedure described above.

FIGS. 32A–C show various alternative embodiments of the presentinvention for the purpose of illustrating the relationship between theultrasound transducer and balloon of the present invention justdescribed above. More specifically, FIG. 32A shows the balloon 820having “straight” configuration with a working length D and a relativelyconstant diameter X between proximal and distal tapers 824,826. As isshown in FIG. 32A, this variation is believed to be particularly welladapted for use in forming a circumferential conduction block along acircumferential path of tissue which circumscribes and transects apulmonary vein wall. However, unless the balloon is constructed of amaterial having a high degree of compliance and conformability, thisshape may provide for gaps in contact between the desiredcircumferential band of tissue and the circumferential band of theballoon skin along the working length of the balloon 820.

The balloon 820 in FIG. 32A is also concentrically positioned relativeto the longitudinal axis of the elongate catheter body 802. It isunderstood, however, that the balloon can be asymmetrically positionedon the elongate catheter body, and that the ablation device can includemore than one balloon.

FIG. 32B shows another assembly according to the invention, althoughthis assembly includes a balloon 820 that has a tapered outer diameterfrom a proximal outer diameter X₁ to a smaller distal outer diameter X₂.(Like reference numerals have been used in each of these embodiments inorder to identify generally common elements between the embodiments.)According to this mode, this tapered shape is believed to conform wellto other tapering regions of space, and may also be particularlybeneficial for use in engaging and ablating circumferential paths oftissue along a pulmonary vein ostium.

FIG. 32C further shows a similar shape for the balloon as that justillustrated by reference to FIG. 32B, except that the FIG. 32Cembodiment further includes a balloon 820 and includes a bulbousproximal end 846. In the illustrated embodiment, the proximate bulbousend 846 of the central region 822 gives the balloon 820 a “pear”-shape.More specifically, a contoured surface 848 is positioned along thetapered working length L and between proximal shoulder 824 and thesmaller distal shoulder 826 of balloon 820. As is suggested by view ofFIG. 32C, this pear shaped embodiment is believed to be beneficial forforming the circumferential conduction block along a circumferentialpath of atrial wall tissue that surrounds and perhaps includes thepulmonary vein ostium. For example, the device shown in FIG. 32C isbelieved to be suited to form a similar lesion to that shown atcircumferential lesion 850 in FIG. 32D. Circumferential lesion 850electrically isolates the respective pulmonary vein 852 from asubstantial portion of the left atrial wall. The device shown in FIG.32C is also believed to be suited to form an elongate lesion whichextends along a substantial portion of the pulmonary vein ostium 854,e.g., between the proximal edge of the illustrated lesion 850 and thedashed line 856 which schematically marks a distal edge of such anexemplary elongate lesion 850.

As mentioned above, the transducer 830 can be formed of an array ofmultiple transducer elements that are arranged in series and coaxial.The transducer can also be formed to have a plurality of longitudinalsectors. These modes of the transducer have particular utility inconnection with the tapering balloon designs illustrated in FIGS. 32Band 32C. In these cases, because of the differing distances along thelength of the transducer between the transducer and the targeted tissue,it is believed that a non-uniform heating depth could occur if thetransducer were driven at a constant power. In order to uniformly heatthe targeted tissue along the length of the transducer assembly, morepower may therefore be required at the proximal end than at the distalend because power falls off as 1/radius from a source (i.e., from thetransducer) in water. Moreover, if the transducer 830 is operating in anattenuating fluid, then the desired power level may need to account forthe attenuation caused by the fluid. The region of smaller balloondiameter near the distal end thus requires less transducer power outputthan the region of larger balloon diameter near the proximal end.Further to this premise, in a more specific embodiment transducerelements or sectors, which are individually powered, can be provided andproduce a tapering ultrasound power deposition. That is, the proximaltransducer element or sector can be driven at a higher power level thanthe distal transducer element or sector so as to enhance the uniformityof heating when the transducer lies skewed relative to the target site.

The circumferential ablation device 800 can also include additionalmechanisms to control the depth of heating. For instance, the elongatecatheter body 802 can include an additional lumen that is arranged onthe body so as to circulate the inflation fluid through a closed system.A heat exchanger can remove heat from the inflation fluid and the flowrate through the closed system can be controlled to regulate thetemperature of the inflation fluid. The cooled inflation fluid withinthe balloon 820 can thus act as a heat sink to conduct away some of theheat from the targeted tissue and maintain the tissue below a desiredtemperature (e.g., 90° C.), and thereby increase the depth of heating.That is, by maintaining the temperature of the tissue at theballoon/tissue interface below a desired temperature, more power can bedeposited in the tissue for greater penetration. Conversely, the fluidcan be allowed to warm. This use of this feature and the temperature ofthe inflation fluid can be varied from procedure to procedure, as wellas during a particular procedure, in order to tailor the degree ofablation to a given application or patient.

The depth of heating can also be controlled by selecting the inflationmaterial to have certain absorption characteristics. For example, byselecting an inflation material with higher absorption than water, lessenergy will reach the balloon wall, thereby limiting thermal penetrationinto the tissue. It is believed that the following fluids may besuitable for this application: vegetable oil, silicone oil and the like.

Uniform heating can also be enhanced by rotating the transducer withinthe balloon. For this purpose, the transducer 830 may be mounted on atorquable member that is movably engaged within a lumen that is formedby the elongate catheter body 802.

Another aspect of the balloon-transducer relationship of the presentembodiment is illustrated by reference to FIGS. 33A–B. In general, as tothe variations embodied by those FIGS., the circumferential ultrasoundenergy signal is modified at the balloon coupling level such that athird order of control is provided for the tissue lesion pattern (thefirst order of control is the transducer properties affecting signalemission, such as length, width, shape of the transducer crystal; thesecond order of control for tissue lesion pattern is the balloon shape,per above by reference to FIGS. 32A–C).

This third order of control for the tissue lesion pattern can beunderstood more particularly with reference to FIG. 33A, which showsballoon 820 to include a shield or filter 860. The filter 860 has apredetermined pattern along the balloon surface adapted to shield tissuefrom the ultrasound signal, for example, by either absorbing orreflecting the ultrasound signal. In the particular variation shown inFIG. 33A, the filter 860 is patterned so that the energy band which ispassed through the balloon wall is substantially more narrow than theband that emits from the transducer 830 internally of the balloon 820.The filter 860 can be constructed, for example, by coating the balloon820 with an ultrasonically reflective material, such as with a metal, orwith an ultrasonically absorbent material, such as with a polyurethaneelastomer. Or, the filter can be formed by varying the balloon's wallthickness such that a circumferential band 862, which is narrow in thelongitudinal direction as compared to the length of the balloon, is alsothinner (in a radial direction) than the surrounding regions, therebypreferentially allowing signals to pass through the band 862. Thethicker walls of the balloon 820 on either side of the band 862 inhibitpropagation of the ultrasonic energy through the balloon skin at theselocations.

For various reasons, the “narrow pass filter” embodiment of FIG. 34A maybe particularly well suited for use in forming circumferentialconduction blocks in left atrial wall and pulmonary vein tissuesaccording to the present invention. It is believed that the efficiencyof ultrasound transmission from a piezoelectric transducer is limited bythe length of the transducer, which limitations are further believed tobe a function of the wavelength of the emitted signal. Thus, for someapplications a transducer 830 may be required to be longer than thelength that is desired for the lesion to be formed. Many proceduresintending to form conduction blocks in the left atrium or pulmonaryveins, such as, for example, less-invasive “maze”-type procedures,require only enough lesion width to create a functional electrical blockand to electrically isolate a tissue region. In addition, limiting theamount of damage formed along an atrial wall, even in a controlledablation procedure, pervades as a general concern. However, a transducerthat is necessary to form that block, or which may be desirable forother reasons, may require a length that is much longer and may createlesions that are much wider than is functionally required for the block.A “narrow pass” filter along the balloon provides one solution to suchcompeting interests.

FIG. 33B shows another variation of the balloon-transducer relationshipin an ultrasound ablation assembly according to the present invention.Unlike the variation shown in FIG. 34A, FIG. 33B shows placement of anultrasonically absorbent band 864 along balloon 820 and directly in thecentral region of the emitted energy signal from transducer 830.According to this variation, the ultrasonically absorbent band 864 isadapted to heat to a significant temperature rise when sonically coupledto the transducer via the ultrasound signal. It is believed that someablation methods may benefit from combining ultrasound/thermalconduction modes of ablation in a targeted circumferential band oftissue. In another aspect of this variation, ultrasonically absorbentband 864 may operate as an energy sink as an aid to control the extentof ablation to a less traumatic and invasive level than would be reachedby allowing the raw ultrasound energy to couple directly to the tissue.In other words, by heating the absorbent band 864 the signal isdiminished to a level that might have a more controlled depth of tissueablation. Further to this aspect, absorbent band 864 may therefore alsohave a width that is more commensurate with the length of thetransducer, as is shown in an alternative mode in shadow at absorbentband 864.

In each of the embodiments illustrated in FIGS. 31A through 33B, theultrasonic transducer had an annular shape so as to emit ultrasonicenergy around the entire circumference of the balloon. The presentcircumferential ablation device, however, can emit a collimated beam ofultrasonic energy in a specific angular exposure. For instance, as seenin FIG. 34A, the transducer can be configured to have only a singleactive sector (e.g., 180 degree exposure). The transducer can also havea planar shape. By rotating the elongate catheter body 802, thetransducer 830 can be swept through 360 degrees in order to form acircumferential ablation. For this purpose, the transducer 830 may bemounted on a torquable member 803, in the manner described above.

FIG. 34B illustrates another type of ultrasonic transducer that can bemounted to a torquable member 803 within the balloon 820. The transducer830 is formed by curvilinear section and is mounted on the inner member803 with its concave surface facing in a radially outward direction. Theinner member 803 desirably is formed with recess that substantiallymatches a portion of the concave surface of the transducer 830. Theinner member 803 also includes longitudinal ridges on the edges of therecess that support the transducer above the inner member such that anair gap is formed between the transducer and the inner member. In thismanner, the transducer is “air-backed.”

This spaced is sealed and closed in the manner described above inconnection with the embodiment of FIGS. 31A–E.

The inverted transducer section produces a highly directional beampattern. By sweeping the transducer through 360 degrees of rotation, asdescribed above, a circumferential lesion can be formed while using lesspower than would be required with a planar or tubular transducer.

The embodiments shown in FIGS. 35A–41 represent variations of thecircumferential ablation device assemblies incorporating ultrasonicablation elements as previously shown and described by reference toFIGS. 31A–34B. These additional embodiments particularly adapt suchultrasound ablation members for use in ablating along a funneling,tapered pulmonary vein ostium or along a posterior left atrial walltissue and surrounding the pulmonary vein's ostium.

FIG. 35A schematically illustrates formation of a lesion through aforward or distal facing wall of a distally tapered balloon 3525 to forma lesion surrounding a pulmonary vein ostium, such as previouslydescribed above for circumferential ablation along a posterior leftatrial wall surrounding a vessel ostium, or otherwise along the ostium.As shown in FIG. 35A, the ultrasonic circumferential ablation deviceassembly 3501 may be adapted to track over a guidewire 3502 and into apulmonary vein. The lesion 3560 surrounding a pulmonary vein ostium 3555to which this embodiment is adapted to form is representative of thoselesions which the other embodiments in FIGS. 16A–30 are also adapted toform. More specifically to this ultrasound variation, transducer 3530 isadapted to send a signal along a circumferential pattern that emits“forward” through the tapered wall of balloon 3525 and into the tissueengaged thereby.

FIGS. 35B–D show a specific mode wherein transducer assembly 3531 has anarcuate, circumferential distal face 3533 that emits a distally orforward oriented circumferential pattern. A pair-shaped ordistally-tapered expandable member 3527 surrounds the transducer andengages the pulmonary vein ostium. The distal end 3529 is adapted toengage the pulmonary vein. The forwardly focused ultrasonic energypasses through the distally tapered wall 3528 of expandable member 3527.In addition, shown schematically such transducer assembly 3531 maycomprise a plurality of flat panels such as at 3532 that areindividually driven. It is contemplated that such arcuate transducercrystal surfaces may require complex poling in the forward or angleddirection desired for emission, as would be apparent to one of ordinaryskill based upon this disclosure.

FIGS. 35E–G show a further variation, wherein the transducer crystal3536 is conically shaped with a distally facing surface 3537 foremitting the desired energy through distally tapered wall 3528 ofballoon 3527. This shape similarly requires poling in the orthogonalplane to the surface for desired ablation. In a further variation, FIG.35H also shows a radially oriented portion of the transducer atcircumferential emitter 3538, which may be described according to priordisclosed designs shown above.

A series of circumferentially spaced ultrasonic panels may also be usedin the circumferential ablation member of the present invention, asshown variously in FIGS. 36A–39B.

FIGS. 36A–C show circumferentially spaced arcuate panels 3630 whichsurround inner member 3611 in radially extended positions such thatdistal surfaces 3632 are pointing toward the region to ablate along adistal aspect of the assembly such as along inner member 3611. FIGS.37A–C show a further variation wherein such ultrasound panels 3730 havea substantially flat shape. In a radially extended position, the flatpanel 3730 presents a distal surface 3732 that is angled toward theregion of tissue to be ablated.

One more detailed construction for such ultrasound transducer panels isshown in FIG. 37D. The ultrasound transducer 3730 is formed from acrystal 3733 having an outer surface 3732 and an inner surface 3735, asdetailed with respect to the cylindrical ultrasound transducerassemblies described in connection with FIGS. 31A–E. An adhesive layermay be applied between the transducer surfaces. Further, an outer jacket3731 may be applied over the to the distal-facing surface of thetransducer panel including the outer surface 3732 of the transducercrystal. Separate electrical leads 3740 and 3741 connect to electrodeson the outer 3732 and inner 3735 surfaces of the transducer. Theultrasound transducer just described is combined with the overall deviceassembly according to the present embodiment as follows. In assembly,the transducer 3730 is desirably “air-backed” to produce more energy andto enhance energy distribution uniformity, as known in the art. In otherwords, the inner surface of the transducer 3735 does not contact anappreciable amount of the proximal surface 3738 of the panel. Theair-backing is maintained by any variety of set-off structures 3736known in the art, such as elastomeric spacers, stand-off's, etc. Inaddition, or in the alternative, a mounting material 3734, including forexample an epoxy a polymeric molded material, may be used to support thetransducer crystal within the panel.

The transducer panels are adjustable from a radially collapsed positionto a radially extended position by use of an expansion member, as shownin various modes by balloon 3825, braided cage 3826, adjustable splines3827, and adjustable stand-off 3828, in FIGS. 38A, 38B, 39A, and 39B,respectively. Actuation of these expansion members can be accomplishedas described elsewhere in this specification in connection with otherembodiments of the present invention.

FIG. 40 shows a further embodiment of an ultrasound ablation device formaking circumferential lesions in the posterior wall of the left atriumaround pulmonary vein(s). A circumferential ablation patternperpendicular to the catheter shaft and ultrasound transducer 4030 isgenerated by deflecting the ultrasound energy using a surface 4004 alonga tapered balloon 4025. Thus, the ultrasound energy is directed toward adistal direction for ablative coupling into tissue contacting thatsurface.

FIG. 41 shows another variation, wherein the radial circumferentialultrasound generated by the ultrasound transducer 4130 is deflected by arearward taper 4106 of the balloon 4125 and toward and through thedistal taper 4108. These last two embodiments may be accomplished forexample by varying the material of the balloon, or by coating theballoon or otherwise providing a material in the described location forultrasonic signal re-direction. Furthermore, such variations may be usedwith other energy sources, such as for example laser energy, which maybe similarly redirected toward a distal balloon taper where itinterfaces with posterior left atrial wall tissue.

It is to be further understood that the various modes of theultrasound-balloon embodiments just illustrated by reference to FIGS.31A–34B may be used according to several different particular methodssuch as those methods otherwise set forth throughout this disclosure.For example, any of the ultrasound transducer embodiments may be used toform a conduction block in order to prevent or treat focal arrhythmiaarising from a specific pulmonary vein, or may alternatively oradditionally be used for joining adjacent linear lesions in aless-invasive “maze”-type procedure.

As discussed above, the embodiments described herein are believed to beparticularly useful in catheter assemblies that are specifically adaptedfor ablating tissue along a region where a pulmonary vein extends from aleft atrium in the treatment of atrial fibrillation. Therefore, theassemblies and methods of the present invention are also contemplatedfor use in combination with, or where appropriate in the alternative to,the various particular features and embodiments shown and described inthe following co-pending U.S. patent applications that also addresscircumferential ablation at a location where a pulmonary vein extendsfrom an atrium: U.S. Ser. No. 08/889,798 for “CIRCUMFERENTIAL ABLATIONDEVICE ASSEMBLY” to Michael D. Lesh et al., filed Jul. 8, 1997; U.S.Ser. No. 08/889,835 for “DEVICE AND METHOD FOR FORMING A CIRCUMFERENTIALCONDUCTION BLOCK IN A PULMONARY VEIN” to Michael D. Lesh, filed Jul. 8,1997; U.S. Ser. No. 09/199,736 for “CIRCUMFERENTIAL ABLATION DEVICEASSEMBLY” to Chris J. Diederich et al., filed Feb. 3, 1998; and U.S.Ser. No. 09/260,316 for “DEVICE AND METHOD FOR FORMING A CIRCUMFERENTIALCONDUCTION BLOCK IN A PULMONARY VEIN” to Michael D. Lesh. Thedisclosures of these references are herein incorporated in theirentirety by reference thereto.

It is further contemplated that the embodiments shown and describedherein may be combined, assembled together, or where appropriatesubstituted for, the various features and embodiments which aredisclosed in the following co-pending provisional and non-provisionalU.S. patent applications: the co-pending non-provisional U.S. PatentApplication for “FEEDBACK APPARATUS AND METHOD FOR ABLATION AT PULMONARYVEIN OSTIUM”, filed on the same day as this Application, and claimingpriority to Provisional U.S. Patent Application No. 60/122,571, filed onMar. 2, 1999; co-pending Provisional U.S. Patent Application No.60/133,610 for “BALLOON ANCHOR WIRE”, filed May 11, 1999; the co-pendingnon-provisional U.S. patent application for “TISSUE ABLATION DEVICEASSEMBLY AND METHOD FOR ELECTRICALLY ISOLATING A PULMONARY VEIN! OSTIUMFROM A POSTERIOR LEFT ATRIAL WALL”, filed on the same day as thisapplication, and which claims priority to Provisional U.S. PatentApplication No. 60/133,677, filed May 11, 1999; the co-pendingnon-provisional U.S. patent application for “APPARATUS AND METHODINCORPORATING AN ULTRASOUND TRANSDUCER ONTO A DELIVERY MEMBER”, filed onthe same day as this application, and which claims priority toProvisional U.S. Patent Application No. 60/133,680, filed May 11, 1999;and co-pending Provisional U.S. Patent Application Ser. No. 60/133,807for “CATHETER POSITIONING SYSTEM”. The disclosures of these referencesare herein incorporated in their entirety by reference thereto.

In addition, a circumferential ablation device assembly according to thepresent invention may be used in combination with other linear ablationassemblies and methods, and various related components or steps of suchassemblies or methods, respectively, in order to form a circumferentialconduction block adjunctively to the formation of long linear lesions,such as in a less-invasive “maze”-type procedure. Examples of suchassemblies and methods related to linear lesion formation and which arecontemplated in combination with the presently disclosed embodiments areshown and described in the following additional co-pending U.S. patentapplications and patents: U.S. Pat. No. 5,971,983, issued on Oct. 26,1999, entitled “TISSUE ABLATION DEVICE AND METHOD OF USE” filed byMichael Lesh, M.D. on May 9, 1997; U.S. Ser. No. 09/260,316 for “TISSUEABLATION SYSTEM AND METHOD FOR FORMING LONG LINEAR LESION” to Langberget al., filed May 1, 1999; and U.S. Ser. No. 09/073,907 for “TISSUEABLATION DEVICE WITH FLUID IRRIGATED ELECTRODE”, to Alan Schaer et al.,filed May 6, 1998. The disclosures of these references are hereinincorporated in their entirety by reference thereto.

While a number of variations of the invention have been shown anddescribed in detail, other modifications and methods of use contemplatedwithin the scope of this invention will be readily apparent to those ofskill in the art based upon this disclosure. It is contemplated thatvarious combinations or subcombinations of the specific embodiments maybe made and still fall within the scope of the invention. For example,the embodiments variously shown to be “guidewire” tracking variationsfor delivery into a left atrium and around or within a pulmonary veinmay be modified to instead incorporate a deflectable/steerable tipinstead of guidewire tracking and are also contemplated. Moreover, allassemblies described are believed useful when modified to treat othertissues in the body, in particular other regions of the heart, such asthe coronary sinus and surrounding areas. Further, the disclosedassemblies may be useful in treating other conditions, wherein aberrantelectrical conduction may be implicated, such as for example, heartflutter. Indeed, other conditions wherein catheter-based, directedtissue ablation may be indicated, such as for example, in the ablationof fallopian tube cysts. Accordingly, it should be understood thatvarious applications, modifications and substitutions might be made ofequivalents without departing from the spirit of the invention or thescope of the following claims.

The following claims are provided to illustrate examples of somebeneficial aspects of the subject matter disclosed herein which arewithin the scope of the present invention.

1. A tissue ablation system for treating atrial arrhythmia by ablating acircumferential region of tissue at a location where a pulmonary veinextends from an atrium, comprising: a delivery member with a proximalend portion and a distal end portion having a longitudinal axis and aradial axis; and a circumferential ablation member coupled to the distalend portion and having a plurality of splines, each with a proximal endportion and a distal end portion, and also having one or more ablationelements each supported along a support region of one of the splines,wherein the plurality of splines are circumferentially spaced around thelongitudinal axis, each of the splines being adjustable between a firstcondition and a second condition wherein the respectively supportedablation element is adjustable between a first radial position and asecond radial position, wherein each spline in the first condition issubstantially radially collapsed and extends substantially along thelongitudinal axis such that the circumferential ablation member isadapted to be delivered through a delivery sheath into the atrium, andin the second condition the support region of each spline extends atleast in part radially away from the longitudinal axis such that each ofthe individual ablation elements is held by the supporting spline in thesecond radial position with the one or more ablation elements beingspaced along a circumferential pattern that surrounds the longitudinalaxis, said circumferential pattern being configured such that the one ormore ablation elements is adapted to engage and ablate thecircumferential region of tissue when the splines are adjusted to thesecond condition at the location, wherein the distal end portion of eachof the splines in the second position has a radius of curvature towardthe longitudinal axis, and wherein each of the splines has a memory tothe second condition.
 2. The system of claim 1, wherein each of thesplines comprises a shape-memory material.
 3. The system of claim 2,wherein each of the splines comprises a nickel-titanium alloy.
 4. Thesystem of claim 1, further comprising an outer member with a proximalend portion and a distal end portion which surrounds the distal endportion of the delivery member, wherein the splines are adapted to bewithdrawn into the outer member in the first position.
 5. The system ofclaim 1 wherein the ablation element comprises an electrical currentablation element.
 6. The system of claim 1 wherein the ablation elementcomprises a thermal ablation element.
 7. The system of claim 1, whereinthe ablation element comprises an ultrasound ablation element.
 8. Thesystem of claim 1, wherein the ablation element comprises a microwaveablation element.
 9. The system of claim 1, wherein the ablation elementcomprises a fluid ablation element.
 10. The system of claim 1, whereinthe ablation element comprises a light emitting ablation element. 11.The system of claim 1, wherein the ablation element comprises anablation means.
 12. A tissue ablation system for treating atrialarrhythmia by ablating a circumferential region of tissue at a locationwhere a pulmonary vein extends from an atrium, comprising: an outerdelivery member with a proximal end portion and a distal end portionhaving a longitudinal axis and a radial axis; an inner delivery memberwith a proximal end portion and a distal end portion, the inner deliverymember being mounted within and coaxial with the outer delivery membersuch that a coaxial space is formed there between; and a circumferentialablation member mounted within the coaxial space coupled to the distalend portion and having a plurality of splines, each with a proximal endportion and a distal end portion, and also having one or more ablationelements each supported along a support region of one of the splines,wherein the plurality of splines are circumferentially spaced around thelongitudinal axis, each of the splines being adjustable between a firstcondition and a second condition wherein the respectively supportedablation element is adjustable between a first radial position and asecond radial position, wherein each spline in the first condition issubstantially radially collapsed and extends substantially along thelongitudinal axis such that the circumferential ablation member isadapted to be delivered through a delivery sheath into the atrium, andin the second condition the support region of each spline extends atleast in part radially away from the longitudinal axis such that each ofthe individual ablation elements is held by the supporting spline in thesecond radial position with the one or more ablation elements beingspaced along a circumferential pattern that surrounds the longitudinalaxis, said circumferential pattern being configured such that the one ormore ablation elements is adapted to engage and ablate thecircumferential region of tissue when the splines are adjusted to thesecond condition at the location, wherein the distal end portion of eachof the splines in the second position has a radius of curvature towardthe longitudinal axis.